The world number one cut short his quarter-final against Holger Rune in the French capital during a second-set tie-break after he lost the opener 6-3 on Friday.
Alcaraz stated after his retirement that it is too early to say whether he will be able to play in the prestigious season-ending tournament in Turin which starts on November 13.
The US Open champion said: "I don't know if I'll make it to the Masters Cup [ATP Finals]. Right now I have to do some tests to see how I am before going to Turin.
"I am focused on trying to improve my abdomen and trying to be 100 per cent in Turin."
The Spaniard felt there was no point in taking any chances.
He added: "At the end of the set, I felt bad. My abdomen was getting bad and I preferred to retire to see it and take care of it.
"I can't stretch. I couldn't serve well, I couldn't hit my forehand and when I turned the body I feel pain, I feel the abdomen in all the movements.
"I was playing thinking about it and feeling the pain, so it was better to withdraw."
Rune will face Felix Auger-Aliassime in his first ATP Masters 1000 semi-final, with both players finishing the season strongly.
Auger-Aliassime beat Frances Tiafoe 6-1 6-4 for his 16th consecutive win to set up a repeat of a final in Basel that the Canadian won last weekend.
Alcaraz was on top for most of his 7-6 (7-1) 7-5 victory, winning 80 per cent of his first-serve points and 75 per cent of net points against Sinner.
Sinner showed determination to stay in both sets, with the Italian saving nine of the 11 break points he faced, but it was ultimately in vain.
The European Open winner will be among those sweating as the race to qualify for the ATP Finals in Turin heats up.
After the win, 18-year-old Alcaraz said: "I'm so happy for this win as Jannik was fighting for a spot at the ATP Finals. It's my third Top 10 win of the year.
"I think Jannik and I will have a great rivalry in the future... I think that I played really, really aggressive, more than him. I think that was one of the keys."
Alcaraz will now face qualifier Hugo Gaston in the next round after the Frenchman impressively knocked out 12th seed Pablo Carreno Busta 6-7 (3-7) 6-4 7-5.
Interesting day for Turin hopefuls
It was a mixed day for others looking to secure a spot at the season-ending ATP Finals later this month as Felix Auger-Aliassime – ranked 12th in the ATP Race to Turin – lost in straight sets to Dominik Koepfer, who added to his impressive list of victims after beating three-time grand slam champion Andy Murray in the first round.
Koepfer will play another Turin hopeful, the 10th-ranked Hubert Hurkacz after he beat Tommy Paul in straight sets.
Cameron Norrie also impressed in his 6-3 6-4 win over Reilly Opelka, which was his 50th tour-level win of the year.
Taylor Fritz awaits after the American stunned fifth seed Andrey Rublev 7-5 7-6 (7-2).
Medvedev and Zverev ease through but Tsitsipas out
Second seed and US Open champion Daniil Medvedev had a routine first match of the tournament as he swept past Ilya Ivashka 7-5 6-4, while Olympic Games gold medallist and fourth seed Alexander Zverev also had few problems against Dusan Lajovic 6-3 7-6 (7-5).
However, third seed Stefanos Tsitsipas exited after retiring hurt with an apparent arm injury against Alexei Popyrin in the first set with the score at 4-2 to the Australian.
Popyrin will now face fellow countryman James Duckworth, who followed up his impressive win against 14th seed Roberto Bautista Agut with a 6-3 3-6 6-3 victory against Lorenzo Musetti.
Elsewhere, 11th seed Diego Schwartzman was shocked by qualifier Marcos Giron 7-6 (7-2) 7-6 (7-4).
There were also wins for 16th seed Grigor Dimitrov against Karen Kachanov, and Sebastian Korda over Marin Cilic.
Gael Monfils will go up against world number one Novak Djokovic in the third round after the experienced French 15th seed came from behind to beat compatriot Adrian Mannarino 2-6 7-6 (7-4) 6-2.
The 19-year-old continues to break records at the top table in tennis, becoming the first teenager to be crowned world number one in the Open Era.
Alcaraz, aged just 19 years and 129 days, also set a new benchmark as the youngest number-one ranked male player in the world since rankings were published in 1973.
Those feats came after winning September's US Open, where he joined Arthur Ashe (1968) and Rod Laver (1969) as the only Open Era players to win on their first or second main-draw outing at the tournament.
Now, Alcaraz has Nadal – a record 22-time major winner – chasing him for top spot, though the youngster assures there will never be bad blood between himself and his compatriot.
"I don't see it that way," Alcaraz responded to Eurosport when asked if he was embroiled in a battle with Nadal.
"It's true, Rafa is fighting for the No.1. Some players have the same goal – to be No.1, so I need to do my best. Outside the court [Rafa and I] are colleagues, at least it's the way I see it.
"Rafa is not my enemy. I say hello, I don't see that competition. With the rest of the players, it's the same. Beyond that relationship, I'll try to keep being No.1."
While Alcaraz remains the world's top-ranked male player, he intends to savour the moment after a surreal victory at the US Open.
"It is an incredible feeling, waking up as No.1, the US Open winner. It's a dream come true," he added.
"I am enjoying this moment so far. I keep working, my life is still the same, I'm still the same kid, same player. I just keep practising, keep improving."
As the teen aims to relish topping the ranks, his next focus turns to the Paris Masters – where he faces Yoshihito Nishioka on Wednesday – with a knee injury not as serious as first thought.
"It's a little pain, but the calendar is very demanding," he said of the injury. "We are playing and travelling with barely any breaks and it's normal that we have a few pains.
"All players have them and we learn how to deal with them. I am feeling good physically and I am ready to play here in Paris and in Turin in the [ATP] Finals."
The world number one suffered an internal oblique muscle tear during a Paris Masters quarter-final against Holger Rune on Friday.
Alcaraz retired early in a second-set tie-break after losing the opening set 6-3 in the French capital.
The US Open champion on Saturday revealed it will take him six weeks to recover from the injury, so Taylor Fritz will take his place in the ATP Finals in Turin next week.
Teenager Alcaraz will also be unavailable for Spain's bid to win the Davis Cup on home soil, with the prestigious event getting under way on November 22 in Malaga.
He posted on Instagram: "After my withdrawal yesterday and having been evaluated by my medical team, Dr Juanjo Lopez and Juanjo Moreno, unfortunately this is the result of my injury: an internal oblique muscle tear in the left abdominal wall with an estimated recovery time of six weeks.
"Unfortunately I won't make the ATP Finals or the Davis Cup Finals. It is tough and painful for me to miss these two events, which are so important to me, but all I can do is be positive and focus on my recovery. Thank you for the support!"
The 19-year-old became the youngest player to top the ATP rankings after winning his maiden major title at Flushing Meadows in September and ends a magnificent season with a record of 57 wins and 13 defeats.
He has won five ATP Tour titles in 2022, with Masters 1000 triumphs in Miami and Madrid along with his finest hour in New York.
After conquering top seed Daniil Medvedev, former world number three Dimitrov recovered from a set down to upstage eighth seed Hurkacz on Thursday.
Norrie shocked 11th seed Diego Schwartzman in straight sets at the ATP 1000 tournament.
DIMITROV CELEBRATES MILESTONE
Bulgarian star and 23rd seed Dimitrov reached his first ATP Masters 1000 semi-final of the season with a 3-6 6-4 7-6 (7-2).
Dimitrov showed he is the comeback king once again, having also saved two break points at 3-3 in the second set.
A semi-finalist at the US Open (2019), Australian Open (2017) and Wimbledon (2014), Dimitrov then squandered a 5-2 lead in the deciding set before eventually prevailing in a tie-break for his 100th Masters 1000 victory.
NORRIE BOOSTS TURIN BID
Norrie's hopes of qualifying for the ATP Finals in Turin received a boost after breezing past Schwartzman 6-0 6-2.
Amid a career-best season, Norrie advanced to his maiden ATP Masters 1000 semi-final, with the 26-year-old to replace Daniel Evans as the new British men's number one.
Seeded 21st, Norrie – who has 45 Tour-level wins in 2021 – now has next month's Finals firmly in sight, having started the day 945 points behind ninth-placed Hurkacz in the race to Turin.
"I have been pretty consistent this year," Norrie said after 74 minutes on court. "I think I am really doing the fundamentals well on serve and return and playing the big points better.
"I have been a little more aggressive and feel I am learning more as I go along and becoming more experienced. We are really happy."
The Serbian makes his first appearance since his US Open final defeat to Daniil Medvedev at the ATP 1000 tournament in the French capital.
That defeat in New York cost Djokovic the chance to become only the third man to win a singles calendar slam by winning all four majors in the same year.
Djokovic also missed the opportunity to move top of the all-time Grand Slam tournament winners list and remains joint-top alongside Roger Federer and Rafael Nadal with 20 titles.
However, the 34-year-old – whose status for the 2021 Australian Open remains unknown – was phlegmatic when he reflected on his loss to Russian world number two Medvedev.
"In a most ideal scenario, I would have won all four of them," Djokovic told a media conference. "Knowing I was so close gives me great encouragement for the future, but it also makes me feel humble about my game, about my career.
"It gives me a kind of reality check where I have to go back to the practice court and really understand what needs to be done so that I could improve.
"This was not an ordinary loss considering the circumstances. I have learned over the years to deal with losses in such way that I treat them as great opportunities for growth.
"I feel that the US Open loss in the final has arrived arguably at the worst or at the best time for me, in a way.
"I'm disappointed that I lost the match, but I feel like I was blessed to experience love from the crowd and support from the stadium that I have never experienced before in my life in New York, and actually not in many places around the world.
"That kind of energy that I received from the crowd from the moment I stepped on the court until I stepped out is a win for life."
Djokovic, who has won four of the last eight Paris Masters tournaments, claimed the prospect of ending the year as the world number one ahead of Medvedev will motivate him.
Should he do so then Djokovic would leapfrog Pete Sampras for the most year-end number one finishes in history with seven.
He will face either Italian Fabio Fognini or Hungarian Marton Fucsovics having received a bye through the first round.
"The year-end number one is on the line between Medvedev and myself, and I'm in a pretty good position," added Djokovic, who has won 85 ATP tour titles.
"That's obviously the goal for the end of the season other than trying to do well in the Davis Cup with the national team. So hopefully I can have a strong finish of the season and clinch that year-end number one.
"I’m pleased to be back. I have been training really well the past couple of weeks. And I have had plenty of success in Paris over the years, so that gives me enough reason to believe that I can do well.
"The lack of match play could be dangerous, so I have to really make sure that I start off my first match very well with a good intensity and build my form."
The world number one is competing in his first tournament since his dream of winning a calendar Grand Slam was ended by Daniil Medvedev in September's US Open final.
After beating Marton Fucsovics in three sets and then benefiting from a walkover against Gael Monfils in the last 16, Djokovic made light work of Fritz in Friday's quarter-final.
He sent down eight aces and was successful with 72 per cent of his first serves that landed on his way to a 6-4 6-3 victory.
However, Djokovic lost his serve on three occasions and, while happy with his overall display, the Serbian feels like there is more to come from his game in the French capital.
"I was absent from the tour for two months coming into this tournament," he said. "The last competitive match I played was in the US Open final, compared to the other guys playing one or two events prior to Paris.
"I knew that I needed to start well, with good intensity and put in a lot of hours on the practice court. But it's different when you play points in a competitive match.
"I am pleased with the way I played against Fucsovics and again today, though I did have ups and downs. I am not entirely pleased with the way I closed out the sets.
"I backed myself up with good returns and read Taylor's serve very well to get into rallies. I closed out the last couple of service games well and that's a positive."
Djokovic is aiming to win the Paris Masters for a record-extending sixth time in his bid to end the year as world number one for a record seventh occasion.
The Serbian will contest his 71st career Masters 1000 semi-final – four short of Rafael Nadal's record – against Hubert Hurkacz, who saw off James Duckworth 6-2 6-7 (4-7) 7-5.
With that victory, the world number 10 clinched the final singles spot at the ATP Finals in Turin later this month.
Hurkacz is the second Polish player to qualify for the event after Wojtek Fibak in 1976. It also means only European players will feature in the ATP and WTA Finals for the first time ever.
Saturday's other semi-final in Paris will be contested between Djokovic's US Open conqueror Medvedev and Olympic gold medallist Alexander Zverev.
Home favourite Hugo Gaston eliminated Pablo Carreno Busta earlier in the tournament but was always likely to face a tougher task against Medvedev.
So it proved, with the qualifier going down 7-6 (9-7) 6-4 in a match that saw Medvedev hit 13 aces to his opponent's one.
"When the atmosphere is against you, you need to face it," Medvedev said. "You need to try to win, no matter what.
"Even when it is against me, I think, 'I will try to beat my opponent and the crowd' because there is no other choice."
Zverev kept his momentum going with a 7-5 6-4 win over Casper Ruud in Friday's final contest, as he made it eight wins on the bounce.
The German held serve throughout, while breaking his opponent twice, to remain on course for a sixth final of 2021.
Djokovic lost to Medvedev in the US Open final in September, with that defeat ending his hopes of a calendar Grand Slam.
But the Serbian, whose semi-final win over Hubert Hurkacz ensured he will be the year-end world number one for a record seventh time, got his revenge in France.
It marks a fifth title of the year and a sixth triumph at this event for Djokovic, who did not compete in the tournament last year – Medvedev winning it in his place.
The 34-year-old had it far from his own way, with Medvedev instantly going a break up, and although Djokovic hit back to draw level at 2-2, the world number two held off a second break point before nosing himself ahead at 4-3.
Yet having served out the first set at the first time of asking, the US Open champion slipped up in the fourth game of the second as Djokovic reeled off some superb returns, and he did not look back.
With the momentum and crowd on his side, Djokovic broke Medvedev twice in quick succession in the decider, and although he was denied claiming the win on his serve, it merely delayed the inevitable.
Medvedev's powerful serve was not enough, with Djokovic keeping his composure to seal a record-setting 37th Masters 1000 title with a sublime forehand into the corner of the court following a draining rally.
Djokovic has played only once on the ATP Tour since losing the US Open final to Daniil Medvedev on September 12.
That defeat at Flushing Meadows ended Djokovic's hopes of achieving a calendar Grand Slam, though the Serbian has returned to action for the final few weeks of the 2021 season.
With the ATP Finals coming up, Djokovic headed to Paris looking to regain the title he claimed in his last appearance in the tournament back in 2019. He needed three sets, but overcame Marton Fucsovics 6-2 4-6 6-3 in his first match.
He has won the Paris Masters on five occasions and is the top seed this time around, with defending champion Medvedev seeded second.
Monfils, seeded 15th, beat Miomir Kecmanovic and Adrian Mannarino en route to the last 16, but confirmed to the media on Thursday that he had been advised not to continue.
Djokovic will face the winner of Cameron Norrie, who recently triumphed at Indian Wells, and Taylor Fritz in the quarter-finals.
The field has already been cleared of third seed Stefanos Tsitsipas, who retired hurt when facing Alexei Popyrin on Wednesday.
Serbian superstar Djokovic scraped past Stefanos Tsitsipas in their semi-final on Saturday, snatching a 6-2 3-6 7-6 (7-4) victory.
Now 19-year-old Danish player Rune awaits the 21-time grand slam winner in Sunday's title match, a clash of generations that is full of promise.
It will be a record 56th Masters 1000 final for Djokovic, and a first for Rune, who will climb to 10th in the world should he win.
Rune is already assured of at least 12th position on the ATP list, a career-high, after knocking out four top-10 players this week: Hubert Hurkacz, Andrey Rublev, Carlos Alcaraz – who retired when trailing in their quarter-final – and Felix Auger-Aliassime, who he beat 6-4 6-2 on Saturday.
In his entire young career before this week, Rune had only beaten four players from the top 10, so this week marks a significant step, no matter how the final goes.
"No doubt that he's the future of the sport, along with Alcaraz and some other guys," Djokovic said. "Hopefully I can suspend his first title Masters 1000 event. We get along really well, good friends off the court.
"Of course on the court, we're competitors. I played him only once, at the last US Open, a good battle, four sets. He has improved a lot, no doubt. He physically is a very fit guy. He's young, so not much to lose. Just swinging through the ball.
"He kind of reminds me of myself, solid backhand and very good defence and just competitive, every point leaving his heart and his legs out there on the court. It's nice to see that. I think he's very good for our sport in general."
Djokovic said it was reassuring to fend off Tsitsipas, who had led by a break in the deciding tie-break.
"It means a lot mentally, emotionally for me, more than anything," said Djokovic. "I need to also make a statement that I'm still there with the young guys, that I'm able to compete with them and win such tight matches."
Six-time champion Djokovic has now reached an eighth final at this tournament, getting to the title match three times more than anyone else, with Boris Becker next on the list with five appearances.
Prior to this week's Masters 1000 event, Djokovic had not played since going down 6-4 6-4 6-4 to world number two Medvedev at Flushing Meadows in September.
That defeat ended Djokovic's hopes of sealing a calendar Grand Slam, but he was in fine form this week as he regained the title he last won in 2019, having not played in the competition last year.
Defending champion Medvedev started the final brilliantly, but Djokovic rallied to win 4-6 6-3 6-3, claiming a record-setting 37th Masters title in the process.
And the world number one explained how he learned from the mistakes he made in New York to prevail this time around, taking his head-to-head record with Medvedev to 6-4 in the process.
"I went back and reviewed the final of the US Open to see what I did wrong and what I did right," Djokovic told the Tennis Channel.
"I tried to read the patterns of his serve and the ball toss, maybe. I tried to look for the small details, because it was a match of small margins."
Reflecting on the showdown in Paris, Djokovic added: "He started better, broke my serve in the first game and I came back. He served the first set out pretty comfortably, but I felt as if I was there.
"I thought it was only a matter of time when I was going to read his serve better and start to make some plays.
"You can't go through him. You have to find a way to play with controlled aggression, play the right shots at the right time and make him come in. It's variety that wins matches against him. We both suffered on the court and there was a lot of gruelling rallies."
Djokovic, who had already secured a record seventh year-end number one, has won 49 matches in 2021, losing on just six occasions.
Victory in Paris would see Djokovic – competing for the first time since September's loss to Daniil Medvedev in the Flushing Meadows final – clinch the year-end number one ranking for a record seventh time.
Djokovic looked to be on course for a routine victory to start his campaign after comfortably taking the first set against Marton Fucsovics in their second-round contest on Tuesday.
However, the top seed's Hungarian opponent fought back to force a decider, hitting 13 winners to seven unforced errors in the second set.
But Djokovic – a record five-time Paris Masters champion – ensured a remarkable turnaround was not forthcoming, breaking Fucsovics twice in the third and, after letting one match point slip, clinching his second to secure victory.
Felix fights back
Ranked 12th in the ATP Race to Turin, Felix Auger-Aliassime needs to lift the trophy in Paris and hope Casper Ruud and Jannik Sinner do not reach the latter stages to make it to the ATP Finals.
Auger-Aliassime risked falling at the first hurdle on Tuesday as the ninth seed was forced to fight back to defeat Gianluca Mager 4-6 6-4 6-1.
"I had difficulty with my pace at the beginning of the match," said Auger-Aliassime. "I didn't hit enough first serves so I had a bit of pressure on my second serve.
"So I could have served better in the first set. I [had] a poor game at four-all and I got broken, but even before that there were moments at 30-all it was a bit hot and a bit tight. I think I relaxed. I found a better pace at the beginning of the second set, and it went even better as the match went forward."
He will next face Dominik Koepfer in the second round following the German's stunning win over Andy Murray on Monday.
Alcaraz sets up Sinner clash
Sinner will have an extremely testing second-round clash after Carlos Alcaraz came from behind to see off wild card Pierre Hugues-Herbert.
Alcaraz let slip a 4-2 lead in the first set to lose that on a tie-break but won six straight points in a second-set breaker before eventually battling to a 6-7 (4-7) 7-6 (7-2) 7-5 win in two hours, 53 minutes.
"It's not easy to play against a home player," Alcaraz said. "I think we played a good level and it was a great match, so I am happy to win. He has a great serve, so I had to return better and remain focus. I think that was the key. I am playing at a good level and I want to finish the year strong."
Diego Schwartzman – the 11th seed – needed three sets to see off John Millman, 15th seed Gael Monfils reversed a one-set deficit against Miomir Kecmanovic and 16th seed Grigor Dimitrov survived a three-setter with Richard Gasquet.
But one seed did fall on Tuesday, Roberto Bautista Agut (14) edged by James Duckworth in three sets.
Djokovic's 12-match winning run looked likely to be halted when Tsitsipas found a mini-break in the decider, with the Greek having fought his way into contention after losing the opening set.
However, the 21-time grand slam champion stepped up when it mattered, winning the final four points of the match to seal a 6-2 3-6 7-6 (7-4) victory.
The Serbian, who will now take part in his record 56th Masters 1000 final on Sunday, opted to praise Tsitsipas for his role in a thrilling encounter following the win.
"It's very sweet, obviously, when you win matches like this against one of the best players in the world," Djokovic said.
"I thought I started the match very well, again, great hitting, like yesterday in the quarters. I had chances early on in the second, I didn't break his serve. The momentum shifted, the crowd got into it. I think he elevated his level of tennis.
"We went into an even battle all the way until the last point, until the last shot. Some incredible points towards the end. I'm just really glad to overcome this challenge."
In Saturday's other match, Rune clinched his first Masters 1000 final appearance by posting a straight-sets victory over Felix Auger-Aliassime.
The in-form Dane seized control of the contest after breaking in the third game of the opener, and did not give up a single break point en route to a comprehensive 6-4 6-2 win.
In doing so, Rune exacted revenge for last week's defeat to Auger-Aliassime in the Swiss Indoors final in Basel, halting the Canadian's 16-match winning run.
Rune has now won eight career matches against top-10 opponents, and half of those victories (four) have come during his strong run in Paris this week.
The world number two has been forced to sit out the first Masters event of the year after not meeting the vaccination requirements to enter the United States, having been deported from Australia ahead of January's Australian Open for similar reasons.
Now, a post on the 20-time grand slam champion's official website suggests he will appear on the clay surface in Monaco, where the 34-year-old resides.
Monaco currently allows those who have recovered from COVID-19 in the previous six months to enter the city-state, with Djokovic claiming to have suffered from the virus in December.
"Novak will open his 2022 clay court season in Monte-Carlo, where he won the Masters 1000 title twice, in 2013 and 2015," the post reads.
The tournament now looks set to be the second to feature Djokovic in 2022 after he lost at the quarter-finals stage of last month's Dubai Tennis Championships.
The Monte Carlo Masters begins on April 10, lasting until April 17, and Djokovic will be looking to make amends after exiting last year's tournament to Dan Evans in the last 16.
Rafael Nadal, who overtook Djokovic for the most men's singles grand slam titles with his January triumph in Australia, holds the record for the most successes in Monaco, winning the tournament on 11 occasions.
Meanwhile, with France having loosened its travel restrictions for unvaccinated people this month, Djokovic will now hope to use the Monaco outing as preparation for a first grand slam appearance of the year at Roland Garros.
The Serbian now looks increasingly likely to be permitted to defend his 2021 French Open title in May after travel restrictions had originally cast doubt on his participation.
Djokovic moved into the last four of a Masters 1000 event for a staggering 74th time with a commanding 6-0 6-3 victory over Musetti on Friday.
The defending champion will do battle with Stefanos Tsitsipas for a place in the final as he eyes a seventh Paris Masters title.
Sixth seed Djokovic made only 10 unforced errors and broke five times, not allowing his Italian opponent to have a game point until early in the second set.
The 21-time grand slam champion only needed 74 minutes to dispatch the unseeded Musetti, moving two victories away from a fifth title of the season.
Meanwhile, world number one Alcaraz's participation in the ATP Finals next week is in doubt after he was injured in his quarter-final against Holger Rune.
Rune won the first set 6-3 and the Dane was 3-1 up in a second-set tie-break when US Open champion Alcaraz brought the match to a premature end.
As Alcaraz prepares to discover whether he can play in the season-ending tournament in Turin, Rune can look forward to facing Felix Auger-Aliassime in his maiden Masters 1000 semi-final.
Auger-Aliassime beat Rune to take the title in Basel last weekend and the Canadian stretched his winning run to 16 matches by beating Frances Tiafoe 6-1 6-4.
Tsitsipas was the last man to seal his place in the semi-finals, getting the better of Tommy Paul, who beat Rafael Nadal earlier in the week, 6-2 6-4.
The state of Victoria, where the year's opening grand slam takes place at Melbourne Park, has introduced a vaccine mandate for professional athletes and across most industries due to the coronavirus pandemic.
The 2021 Australian Open went ahead, albeit in February instead of January, and without fans for most of the tournament following a snap lockdown of Melbourne due to COVID-19.
Last week, Australia prime minister Scott Morrison said unvaccinated players would be allowed to contest the slam if they completed two weeks in quarantine, though Victoria premier Dan Andrews dismissed those comments, insisting athletes would not be granted access unless they received the COVID-19 vaccine.
A record nine-time Australian Open champion, world number one Djokovic remains non-committal over his looming title defence.
"Well, I'm going to decide on whether I go to Australia or not after I see the official statement from Tennis Australia," Djokovic said as he prepares for the Paris Masters – his first tournament since losing to Daniil Medvedev in September's US Open final.
"Right now, we don't have any official announcement or statement. So until that's out, I won't be talking about this anymore, because I don't want to be part of the stories about the assumptions and what-ifs.
"When official condition requirements to travel to Australia and play in Australia are out, then obviously I'll see what I personally do with that, and also the bigger group of the players, you know, because the situation is obviously different in Australia than most parts of the world."
World number two Medvedev also refused to confirm his Australian Open participation.
"I always said it, that I really like Novak's answer about this. I want to keep my medical, no matter if it's about vaccine, leg injury, head injury... I want to keep my medical private for a reason," Medvedev said.
"I feel like tennis is such a brutal sport where you're always one on one against your opponent, and any information you give him can go against you.
"If you're playing Australia, it's obvious you're vaccinated. So that's why I said I'm willing to play Australia, but I won't say if you'll see me there, but we're going to see in January."
For Djokovic, a 10th win in a row came in an absorbing battle with his Paris-born American opponent Maxime Cressy, who displayed a typically aggressive approach on serve, with 15 aces and 10 double faults overall.
Djokovic was strong on his own delivery, however, with the Serbian losing just six points on serve and not facing a break point on his way to a 7-6 (7-1) 6-4 victory.
"I'm happy with the way I played," Djokovic said. "When chances were presented, I was able to use them, even though I did have some missed break points.
"But it was very challenging, first match with a guy who serves extremely well and strong and fast.
"He's comfortable coming to the net. It's nice to see. I think he's the only guy that really comes to the net after every first and second serve. I think it's good for tennis to see that, particularly in these modern times when most of the players are playing from back of the court. He's a very athletic guy.
"It's difficult to play him definitely in these kind of conditions where balls are flying through the court and it's quicker than it was last year. So tough to break.
"But I didn't make too many unforced errors. I'm very pleased with the way I served, with the way I was holding my service games. Just the way I felt, the way I played, it was all positive."
Third seed Ruud ground out a 6-1 7-6 (9-7) victory against Frenchman Richard Gasquet, with the Norwegian saving three of four break points in what proved to be a tightly fought contest.
Mistakes from Gasquet were ultimately costly, the veteran having 10 unforced errors in the second set compared to Ruud's two.
Seventh seed Andrey Rublev was also victorious, the Russian winning 6-2 6-3 against American John Isner, while the British duo of Jack Draper and Dan Evans progressed to the last-32 stage, beating Arthur Rinderknech and Brandon Nakashima respectively.
Halep and Kerber will miss the WTA Premier Mandatory tournament in Indian Wells due to injuries, it was announced on Friday.
Indian Wells champion in 2015, world number two Halep cited a foot injury for her withdrawal.
Kerber – a three-time grand slam champion – succumbed to an ongoing left leg problem, replaced in the main draw by Taylor Townsend.
"I'm incredibly disappointed to have to withdraw from the 2020 BNP Paribas Open. Unfortunately the foot injury that I picked up before Dubai is still causing me trouble and I will be unable to recover in time to travel to Indian Wells," Halep, the two-time major champion, said.
"It is without doubt one of the highlights of the tennis calendar for me and I will be really sad to miss it, but I'm already looking forward to being back in 2021!"
Bianca Andreescu won Indian Wells last year and the US Open champion could still defend her title, despite injuries preventing her from playing in 2020.
A day on from beating Feliciano Lopez for his 1,000th ATP Tour-level victory, Nadal saw off Jordan Thompson in straight sets on Thursday.
The Spaniard lost just 12 points on his serve in his first meeting with world number 61 Thompson, who hauled down his racket after failing to win a set point in the second, which Nadal subsequently won on a tie-break.
Yet despite another impressive showing in Bercy, Nadal believes he still has work to do if he is to overcome compatriot Busta, who beat Norbert Gombos 7-5 6-2.
"I want to improve everything, always," the world number two said after his 6-1 7-6 (7-3) triumph. "But that's the work of every day, no? Try to fix the things that I think I can do it better, and hold the things that I am doing well, no?
"So I think I am not doing a lot of things bad. I just didn't play in indoors for a year almost, and is part of the process of course. I need to keep going. I think these kind of matches helps. Yesterday's match, today's, tomorrow is another opportunity.
"These matches are an important test for me to keep improving, so I really believe and hope that it's going to help me to improve. I think I'm playing well. I just think I need to win more matches on this surface.
"I need to be ready to play my best against an opponent that I know is playing well and with confidence. I hope to be ready to play my game and really read well, because that's what I'm going to need."
WAWRINKA AND ZVEREV BATTLE THROUGH
Nadal is into the Paris Masters quarters for an eighth time but the 34-year-old has only reached the final on one previous occasion, losing to David Nalbandian in 2007.
Should he overcome his compatriot Busta on Friday, one of Alexander Zverev or Stan Wawrinka await in the semi-finals.
Fourth-seeded Zverev needed three hours to overcome unseeded Adrian Mannarino 7-6 (13-11) 6-7 6-4, saving set points in each of the first two sets.
Zverev wasted a set point of his own in a tie-breaker as the German was taken all the way to a decider, which he won by breaking Mannarino in the ninth game.
Chasing a third title of the year, Zverev will now face Wawrinka in the last eight after the Swiss battled from behind to beat Andrey Rublev 1-6 6-4 6-3.
Rublev broke his opponent three times to take the first set inside 32 minutes, but Wawrinka held in the second to level up a match that went on past midnight local time.
World number eight Rublev had won 11 matches in a row but he struggled to cope with Wawrinka in the third set, losing serve in the first and ninth games to bring his participation to an end.
As he prepares for a title defence at the Paris Masters, the 21-time grand slam winner is naturally out to put the frighteners up his rivals.
But when asked on Sunday whether he was "the monster of tennis", because of his strong track record against the cream of the sport, Djokovic had to smile and laugh it off.
"The monster? I don't know the significance of that word in your language, but in mine it is not really the best," he said in a press conference.
"I prefer not to be the monster of the tennis. But yeah, the record against pretty much all the top players is positive, which is great.
"We played so many tournaments throughout the year and throughout our careers, and some of us have been there more than some of the younger players. So playing more matches helps, I think, to know how to approach every next big challenge when you play one of your top rivals.
"I have managed to do well throughout my career, which is great, which is something that I always intended to do."
Djokovic earned a 27-23 win-loss record in his favour against Roger Federer and he leads Rafael Nadal 30-29 and is 25-11 up on Andy Murray across their tour careers.
He has lost his lone meeting with new world number Carlos Alcaraz, which came on clay in the Madrid semi-finals earlier this year, and there could be more such clashes during the final years of Djokovic's career.
At the age of 35, Djokovic remains a force to be reckoned with. He gets a first-round bye in Paris and will face Maxime Cressy or Diego Schwartzman in his opening match
The world number seven has won his last three singles tournaments, with a triumph at Wimbledon followed by titles at Tel Aviv and Astana.
Djokovic has six Paris Masters titles, the joint-most he has managed at any of the ATP 1000 events, level with his haul from Miami and the Internazionali d'Italia.
His ranking is unusually low, and that can to a large extent be attributed to him being prevented from playing in Australia and North America this season, due to his refusal to accept a COVID-19 vaccination.
Djokovic also suffered from Wimbledon being stripped of ranking points amid the Ukraine crisis, meaning that despite successfully defending his title at the All England Club, he lost the 2,000 ranking points he collected at the grand slam in the 2021 season.
He said his experience after being banished from Australia in January was "challenging".
"It was a completely new experience for me," Djokovic added. "Unfortunately not a great one but still a life experience, and a possibility for me to grow stronger out of that."
