Two-time major winner Victoria Azarenka says it is "bizarre" that fans need to be vaccinated to attend the US Open but not the players.

The 2021 US Open marks the first tennis tournament where fans must show their proof of COVID-19 vaccination in order to attend matches inside the Flushing Meadows venue. The decision was made less than 72 hours prior to the first matches at the US Open.

Azarenka, who defeated Italian Jasmine Paolini 6-3 7-6 (7-1) in the second round on Wednesday, said there was a double standard applied for fans compared to players who are not required to be vaccinated to play.

"I want to start this conversation between our players, because to me that's a bit bizarre that fans have to be vaccinated and players are not," three-time US Open finalist Azarenka told reporters.

"I think it's inevitable that it will be mandated at some point, like other leagues are doing.

"I don't see the point of stalling it, because I think we all want to be safe, we all want to continue doing our jobs, and I know there is a lot of discussions about it."

She added: "I hope that as an association we make the best decision for our business, for our health, for the tournaments and for the public."

On Saturday, Briton Andy Murray voiced his opinion that players need to be vaccinated, saying it is their responsibility as they travel the world to play.

Numerous top players including Novak Djokovic, Stefano Tsitsipas and Daniil Medvedev have previously spoken about their concerns about getting vaccinated.

Medvedev would not be drawn on Azarenka's comments after he defeated Dominik Koepfer 6-4 6-1 6-2 in the second round on Wednesday.

"Tough to answer this question," Medvedev told reporters. "I think everybody can have his own opinion.

"I understand why they did it to the fans. So far it has not been applied to the players. We as players, we can just follow the guidelines and the rules. That's all we can do.

"I think it's not for players to decide, because that's why we have governing bodies in tennis."

Stefanos Tsitsipas has defended his "personal need" for long bathroom breaks after being jeered during his four-set second round win over Adrian Mannarino at the US Open on Wednesday.

The world number three triumphed 6-3 6-4 6-7 (4-7) 6-0 but was booed by the Arthur Ashe Stadium crowd after taking a bathroom break which exceeded seven minutes.

The Greek was criticized by Andy Murray, who said he lost respect for Tsitsipas after taking a lengthy break ahead of the final set in their five-set first round epic on Monday.

Alexander Zverev weighed in on the discussion, claiming Tsitsipas was communicating with his coach during his bathroom breaks, labelling them "ridiculous" and saying he had broken an "unwritten law".

Tsitsipas reverted to the rule book in his defence after beating Mannarino, insisting he had done nothing illegal and longer breaks were part of his "personal needs".

"It's just my personal needs," Tsitsipas told reporters. "Some people have other needs. Some people take much more than 25 seconds between points, which is fair.  

"I've done everything the right way. If I haven't I should be penalized. I completely agree with it. I should get a fine or be penalized if I haven’t followed whatever I've done correctly. But as far as I know, it is a necessity, it is a need when I'm out there playing and performing."

Tsitsipas said he felt fans who booed and jeered did not understand the game or his need to take longer bathroom breaks.

"I haven’t done anything wrong so I don't understand," he said. "The people love the sport, they come to watch tennis. I have nothing against them. But some people don't understand. They haven't played tennis at high level to understand how much effort and how much difficult it is to do what we are doing."

He added: "It is important. First of all, you carry less weight on you with all the sweat. You feel rejuvenated, you feel fresh, and you don't have all the sweat bothering you and coming in your face, on your fingers, everywhere all over your body. It makes you feel better.

"For me it is important to take that break. For someone else probably not. And everyone has his own time. I try and be as quick as I can. Sometimes I just need a bit more time."

Tsitsipas added that he was taken aback by the public criticism from Murray and Zverev.

"I never complain of what other players do," the 23-year-old French Open runner-up said. "My parents have taught me not to watch other people's business and concentrate on myself. Do my job.

"I just don’t understand when some players go and criticize other players, or during a match they put too much emphasis on it."

There have been calls for a hard cap on the permitted time for bathroom breaks, which American Sloane Stephens agreed with, speaking after her straight-sets win over 21st seed Coco Cauff.

"I don't think you should be gone from the court for six-eight minutes," Stephens said. "It's a long time to leave a match. That changes the whole momentum of a match.

"I can't speak for what happened in that match, but I do know on the girls' side, there still is a lot of that. It's gamesmanship.

"I think there definitely needs to be a rule or changes. They make a lot of rule changes for smaller things, like they took one minute off the warmup. If someone goes to the bathroom for nine minutes, no one says anything."

Two-time major winner Victoria Azarenka says it is "bizarre" that fans need to be vaccinated to attend the US Open but not the players.

The 2021 US Open marks the first tennis tournament where fans must show their proof of COVID-19 vaccination in order to attend matches inside the Flushing Meadows venue. The decision was made less than 72 hours prior to the first matches at the US Open.

Azarenka, who defeated Italian Jasmine Paolini 6-3 7-6 (7-1) in the second round on Wednesday, said there was a double standard applied for fans compared to players who are not required to be vaccinated to play.

"I want to start this conversation between our players, because to me that's a bit bizarre that fans have to be vaccinated and players are not," three-time US Open finalist Azarenka told reporters.

"I think it's inevitable that it will be mandated at some point, like other leagues are doing.

"I don't see the point of stalling it, because I think we all want to be safe, we all want to continue doing our jobs, and I know there is a lot of discussions about it."

She added: "I hope that as an association we make the best decision for our business, for our health, for the tournaments and for the public."

On Saturday, Briton Andy Murray voiced his opinion that players need to be vaccinated, saying it is their responsibility as they travel the world to play.

Numerous top players including Novak Djokovic, Stefano Tsitsipas and Daniil Medvedev have previously spoken about their concerns about getting vaccinated.

Medvedev would not be drawn on Azarenka's comments after he defeated Dominik Koepfer 6-4 6-1 6-2 in the second round on Wednesday.

"Tough to answer this question," Medvedev told reporters. "I think everybody can have his own opinion.

"I understand why they did it to the fans. So far it has not been applied to the players. We as players, we can just follow the guidelines and the rules. That's all we can do.

"I think it's not for players to decide, because that's why we have governing bodies in tennis."

Naomi Osaka was due to face Olga Danilovic on Wednesday, but the defending US Open champion was handed a walkover into the third round. 

Osaka, who defeated Marie Bouzkova in the first round to start her title defence at Flushing Meadows, is hunting her fifth grand slam title and third in New York. 

Serbian youngster Danilovic, who is being mentored by ATP world number one Novak Djokovic, defeated American Alycia Parks in straight sets on Monday but had to pull out of her second-round tie with Osaka due to a viral illness. 

However, the 20-year-old stressed she had not tested positive for COVID-19. 

"Hi everyone… I am so sad to have to withdrawal [sic] from my match this morning. I have been feeling unwell these past few days dealing with a non-COVID related viral illness," Danilovic wrote in an Instagram post. 

"I was really looking forward to playing against Naomi on Arthur Ashe Stadium today, but [it was] not to be this time. 

"I just want to say [a] big thank you to medical staff here [at the] US Open and [to] everyone for your support and I cannot wait to be back in New York at this amazing tournament next year." 

Osaka will face Leylah Fernandez in the third round on Friday after the Canadian beat Kaia Kanepi 7-5 7-5. 

Another of the big names, Simona Halep, also progressed, with the two-time grand slam winner seeing off Kristina Kucova 6-3 6-1. 

Novak Djokovic's quest to become only the third man to complete a calendar Grand Slam and first to win 21 majors started with a 6-1 6-7 (5-7) 6-2 6-1 victory over Holger Rune at the US Open.

Not since Rod Laver in 1969 has a man won all four majors in the same year – Djokovic arrived in New York as the Australian Open, French Open and Wimbledon champion.

Also eyeing history as the first man to claim 21 slams – currently tied with injured superstars Rafael Nadal and Roger Federer – Djokovic navigated his passage through to the second round at Flushing Meadows on Tuesday.

Danish qualifier Rune was making his grand slam main-draw debut, but the 18-year-old was not overawed under the bright Arthur Ashe lights.

However, Rune faded fast due to apparent cramps as world number one Djokovic eventually cruised through to round two of the year's final major after more than two hours.

Playing for the first time since his Golden Slam bid came unstuck at the Olympic Games in Tokyo, Djokovic looked comfortable initially, closing out a merciless opening set with an ace.

Djokovic did not face a break point, boasting 100 percent returns against first serve, barely giving Rune a break.

But that changed in the second set – the energetic Rune winding up the crowd as he raced out to a 3-0 lead before Djokovic swiftly reeled off four consecutive games to move ahead.

Rune, however, capitalised on some uncharacteristic double faults to ultimately level the match in a tie-break, much to the delight of the American crowd.

But that is as good as it got for a frustrated Rune, whose physical conditioning proved his downfall, having gone toe-to-toe with the top seed in a fearless display.

Data slam: Djokovic extends US Open streak

Back in New York for the first time since he was sensationally thrown out of the US Open last year after accidentally hitting a line judge in the throat with a tennis ball, Djokovic got the job done.

Three-time US Open champion Djokovic now remains unbeaten in opening-round matches at the tournament, with a 16-0 record.

WINNERS/UNFORCED ERRORS

Djokovic – 55/30
Rune – 24/26

ACES/DOUBLE FAULTS

Djokovic – 17/7
Rune – 1/4

BREAK POINTS WON

Djokovic – 8/14
Rune – 2/3

World number one Ash Barty was relieved but happy with her response after surviving a first-round scare against Vera Zvonareva at the US Open.

Barty – the top seed back at Flushing Meadows after skipping the 2020 event due to the coronavirus pandemic – booked her spot in the second round with a 6-1 7-6 (9-7) victory but the Wimbledon champion endured a challenging opener in New York on Tuesday.

Despite firing down 11 aces to improve her WTA Tour-leading tally to 300 in 2021, and hitting 31 winners, veteran Zvonareva was a tricky first-up opponent for Australian star Barty.

A US Open and Wimbledon runner-up in 2010, Zvonareva made life difficult for Barty in the second set, earning a chance to force a decider but the 36-year-old was unable to capitalise at 7-6 in the tie-break.

Afterwards, Barty – who ranks first this season for titles (five), match victories (41), finals reached (six) and top-10 victories (seven) – told reporters: "Obviously a tough one against Vera straight up.

"She's an experienced campaigner. She knows how to get herself into matches. I think all in all, adapting to conditions was a little bit slower than I probably would have liked [but] we're through. We have another chance to improve on that in the next round.

"I think when my back was against the wall late in that buster, I came up with some really good stuff. That's all we can ask is when your back is against the wall, you trust yourself, you go out there and pick your spots and hit them."

Two-time grand slam champion Barty – fresh off winning in Cincinnati as Clara Tauson awaits in round two – added: "It obviously got really tense in that second set - tight - and in the bigger moments I was able to be aggressive and trust myself and that was a massive thing today.

"There were a couple of games where I had lapses in concentration but I was able to come through in straight sets and now we go back to the drawing board, work on a few things and we'll be as happy as Larry.

"I'm certainly happy to be through and playing again here in New York."

Alexander Zverev has accused Stefanos Tsitsipas of behaving like a junior and disrespecting his opponents by taking such long bathroom breaks during matches.

Andy Murray was furious when Tsitsipas was off court for around eight minutes ahead of the final set in their thrilling first-round match at the US Open on Monday.

Tsitsipas also required a medical timeout for a foot problem during a pulsating contest that the world number three won 2-6 7-6 (9-7) 3-6 6-3 6-4 at Flushing Meadows.

Murray said he had lost respect for the 23-year-old, who defended his lengthy spell off court and stated he had played by the rules.

The Brit was in no mood to back down on Tuesday, however, as he tweeted: "Fact of the day. It takes Stefanos Tsitsipas twice as long to go the bathroom as it takes Jeff Bezos to fly into space. Interesting."

Zverev appeared to accuse Tsitsipas of communicating with his father and coach, Apostolos, when he took a break during their semi-final showdown at the Western and Southern Open in Cincinnati this month.

Tsitsipas responded by denying having ever used his phone during such a situation, describing the accusation as "absolutely ridiculous."

However, world number four Zverev had Tsitsipas in his sights once again after beating Sam Querrey 6-4 7-5 6-2 in New York.

The German said: "It's happening every match. It's not normal. It happened to me in the French Open, to Novak at the finals [of the] French Open. I think Hamburg against [Filip] Krajinovic he was complaining, against me in Cincinnati was ridiculous, and now here again. I think players are catching up with that.

"He's the number three player in the world. I do not believe he needs to do that, because if you're top three in the world, you're one of the best in the sport.

"These kind of things happen at junior events, at Futures, at Challengers maybe, but not when you're top three in the world.

"You're allowed to do that but it's like an unwritten rule with players. I have been breaking rackets, I go insane sometimes and all that but one thing I'm very proud of, and I'll keep for the rest of my career, is I win and I lose by playing tennis on the tennis court."

Zverev reiterated his grievance with Tsitsipas having taken such a lengthy break during their meeting in Cincinnati.

"I didn't ask that question in Cincinnati, which I was very surprised at, because I was going to answer that very truthfully and honestly," he said.

"He's gone for 10-plus minutes. His dad is texting on the phone. He comes out and all of a sudden his tactic completely changed. It's just not me but everybody saw it. The whole game plan changes.

"I'm like, either it's a very magical place he goes to or there is communication there. But I also don't want to disrespect him. He is a great player, he is number three in the world for a reason. He's winning tournaments and playing incredible tennis this year for a reason, so it's not only that.

"But I do believe, and Andy said it as well, there is some level of respect that everybody needs to have between players.

"I feel like sometimes - or he might just go to the toilet. We don't know that, that's also possible. But it just happens too often, I would say."

Andy Murray has doubled down on his criticism of Stefanos Tsitsipas by joking that his US Open conqueror's bathroom breaks take twice as long as Jeff Bezos' trips to space.

World number three Tsitsipas beat Murray 2-6 7-6 (9-7) 3-6 6-3 6-4 in a thrilling five-set battle in the opening round at Flushing Meadows on Monday.

The opening-day showdown was overshadowed by Tsitsipas' controversial bathroom break ahead of the decisive fifth set – the Greek star spending around eight minutes off court, much to the frustration of Murray.

Tsitsipas also required a medical timeout for an apparent foot problem after losing the third set to 2012 champion Murray, who was far from impressed following almost five hours of action.

Speaking after the match, Murray – who failed to progress beyond the first round of the US Open for the first time in 15 appearances – said he had lost respect for Tsitsipas and suggested his opponent had deliberately attempted to disrupt his flow. 

Tsitsipas defended his lengthy break, insisting he had played by the rules and that he would speak to Murray face-to-face should the Briton wish to take the issue further.

Rather than resolving the matter, however, Murray aimed another dig at Tsitsipas with a sarcastic message on his personal Twitter account on Tuesday, comparing the stoppage to the 10 minutes and 10 seconds it took billionaire Bezos to fly to space last month.

"Fact of the day. It takes Stefanos Tsitipas (sic) twice as long to go the bathroom as it takes Jeff Bazos (sic) to fly into space. Interesting," he posted.

With the win over Murray, Tsitsipas became the 10th active player to defeat all four members of the 'Big Four' – Murray, Novak Djokovic, Rafael Nadal and Roger Federer.

Tsitsipas will meet world number 44 Adrian Mannarino in the second round on Wednesday.

Defending US Open champion Naomi Osaka passed her opening-round test, producing a powerful performance against Marie Bouzkova 6-4 6-1 on Monday.

All eyes were on Osaka following a difficult couple of months due to mental health concerns as a result of "long bouts of depression" since winning the 2018 US Open.

Osaka withdrew from May's French Open having won her first-round match, after she was fined and threatened with further punishment – and possible expulsion from the grand slam – for skipping obligatory media duties.

The Japanese star subsequently pulled out of Wimbledon before returning for the Olympic Games, though she suffered a surprise loss on home soil in Tokyo and was reduced to tears during a news conference in Cincinnati.

But as fans returned to Flushing Meadows for the first time in two years after the 2020 event was played behind closed doors due to the coronavirus pandemic, Osaka looked comfortable under the Arthur Ashe Stadium lights with the likes of former heavyweight champion Mike Tyson and Hollywood star Alec Baldwin in the crowd.

Bouzkova kept pace with Osaka in the opening set, not overawed by the occasion, but she came unstuck on serve in the 10th game.

While fending off one set point, Bouzkova was unable to save another, slicing a backhand into the net as Osaka closed out the set on her opponent's racquet.

With a set under her belt having reeled off 21 winners in the opener, Osaka stepped it up a gear – winning seven consecutive games before Bouzkova avoided a bagel.

Bouzkova continued to battle but it only delayed the inevitable as Osaka continued her quest for a fourth US Open crown and fifth slam title.

Data slam: Osaka on track to follow in Serena's footsteps

The 23-year-old needed one hour, 33 minutes to book her spot in the next round. Osaka is looking to become the first woman to win consecutive titles at Flushing Meadows since 23-time major champion Serena Williams claimed three in a row from 2012 to 2014.

Osaka is the only woman to win at least one major title over the past four seasons, claiming the Australian Open in 2019 and 2021, as well as the US Open in 2018 and last year.

WINNERS/UNFORCED ERRORS

Osaka – 34/23
Bouzkova – 10/8

ACES/DOUBLE FAULTS

Osaka – 4/1
Bouzkova – 2/2

BREAK POINTS WON

Osaka – 3/6
Bouzkova – 0/8

Andy Murray said he has lost respect for Stefanos Tsitsipas in a scathing criticism of the world number three's excessively long bathroom break at the US Open.

Tsitsipas rallied past three-time grand slam champion Murray 2-6 7-6 (9-7) 3-6 6-3 6-4 in a thrilling five-set battle in the opening round of the major at Flushing Meadows on Monday.

Murray's career has been devastated by injuries – the 34-year-old underwent hip resurfacing in 2019 but he has continued to be plagued by fitness problems – however he turned back the clock in a heroic display on Arthur Ashe Stadium, where the former world number one led two sets to one before Tsitsipas' comeback.

But the opening-day showdown was overshadowed by Tsitsipas' controversial bathroom break at the end of the fourth set – the Greek star spent around eight minutes off court, much to the frustration of Murray.

Tsitsipas also required a medical timeout for an apparent foot problem after losing the third set to 2012 champion Murray, who was far from impressed following almost five hours of action.

"It can't be a coincidence that it's happening at those moments. I don't believe it [Tsitsipas' foot] was causing him any issue at all," said world number 112 Murray after failing to progress beyond the first round of the US Open for the first time in 15 appearances.

"The match went on for another two-and-a-bit hours after that. He was fine, moving great I thought. It's just disappointing because I feel it influenced the outcome of the match. I'm not saying I necessarily win that match [without Tsitsipas' delays], for sure, but it had influence on what was happening after those breaks.

"I rate him a lot. I think he's a brilliant player. I think he's great for the game. But I have zero time for that stuff at all, and I lost respect for him."

"If people don't care enough about it to change, that's fine," Murray said of players taking long breaks.

"Look, I'll speak to my team about it. I'll listen to what, I don't know, fans, players and everything are saying about it. Maybe I'm being unreasonable. Maybe I'm overreacting to something because I lost the match.

"But yeah, right now sitting here I feel like it's nonsense and they need to make a change because it's not good for the sport, it's not good for TV, it's not good for fans. I don't think it's a good look for the players either.

"I'm sitting in here after a match like that against one of the best players in the world, and rather than talking about how fantastic he is, how good he is for the game, how great it was for me that I was able to put on a performance like that after everything that's gone on the last four years – I'm sitting in here talking about bathroom breaks and medical timeouts and delays in matches.

"That's rubbish, I don't think that that's right. I said I don't want to do press tonight because I know I'm going to sit here and it's going to seem like I'm just smashing him. Yeah, that's annoying for me because sounds like sour grapes because you've lost a match and everything.

"I would have said the same thing if I'd won, I promise. It was nonsense, and he knows it."

Stefanos Tsitsipas was able to breathe a sigh of relief on Arthur Ashe Stadium after the third seed rallied past former world number one Andy Murray 2-6 7-6 (9-7) 3-6 6-3 6-4 in a thrilling five-set battle.

French Open runner-up Tsitsipas and 2012 champion Murray was one of the standout matches in the opening round at Flushing Meadows and the near-five-hour showdown did not disappoint as the latter turned back the clock in New York on Monday.

Murray's career has been devastated by injuries – the 34-year-old underwent hip resurfacing in 2019 but he has continued to be plagued by fitness problems.

However Murray, who only had one pair of shoes, soaking wet with sweat, took a positive approach from the start and earned a surprise two-sets-to-one lead against the slam hopeful.

Murray, though, was made to rue his inability to capitalise on two set points at 6-4 in the second-set tie-break – leaving the door open for world number three Tsitsipas.

Tsitsipas held his nerve as the prospect of a first-round boilover beckoned, but it was not without controversy after the Greek star took his time in the bathroom between the fourth and fifth seeds, frustrating Murray.

It is the first time in 15 US Open appearances world number 112 Murray lost in the opening round in New York.

"It is not easy," Tsitsipas – who celebrated his ATP Tour-leading 49th victory of the year – said in his on-court interview. "I had to make lots of sacrifices to come back.

"I think the atmosphere was great today, with a lot of positive tennis. The New York crowd is known to be one of the best crowds in the world.

"The fact we are able to compete out here with an electric crowd today is something we have been waiting for."

Tsitsipas, who will meet Adrian Mannarino in the second round, added: "I hope I am able to keep my game at the same level as I managed today.

"Hopefully I will be back here on this court."

Novak Djokovic is a strong favourite to become only the third man to complete a calendar Grand Slam and make history at the US Open.

Djokovic has won all three majors this year and can complete a 2021 clean sweep at Flushing Meadows.

The irrepressible world number one would also go beyond Roger Federer and Rafael Nadal – both absent due to injury – with 21 grand slam singles titles if he triumphs in New York.

There will be no elusive record-equalling 24th major singles crown for Serena Williams, who has not recovered from the hamstring injury she suffered at Wimbledon.

With Ash Barty and Naomi Osaka the leading contenders to take the women's singles title, Stats Perform use Opta data to preview the final grand slam of the year.

WHAT A DIFFERENCE A YEAR MAKES FOR DOMINANT DJOKOVIC

Djokovic was thrown out of the US Open last year after accidentally hitting a line judge in the throat with a tennis ball.

The 34-year-old arrived in New York in far better spirits than when he left last September, having taken on all comers this year.

Djokovic missed out on a Golden Slam when he failed to win Olympic gold in Tokyo, but he could join Don Budge (1938) and Rod Laver (1962 and 1969) as the only men to win all four majors in the same year.

Maureen Connolly (1953), Margaret Court (970) and Steffi Graf (1988) are the only women to achieve the incredible feat.

BARTY TO GO BACK-TO-BACK?

Barty became the first Australian woman to win a Wimbledon singles title for 41 years in July.

Not since Williams in 2012 has a player claimed back-to-back women's singles major crowns in the same year, but Barty could take some stopping.

She could become the ninth woman in the Open Era to win Wimbledon and the US Open in the same season. 

Margaret Court, Billie Jean King, Chris Evert, Martina Navratilova, Steffi Graf, Martina Hingis, Venus Williams and Serena Williams can boast that achievement.

OSAKA BACK TO DEFEND TITLE

Japanese sensation Osaka won her third grand slam title at Flushing Meadows last September and went on to add a fourth at the Australian Open this year.

Osaka returns to grand slam action for the first time since withdrawing from the French Open, citing struggles with her mental health.

The world number three could be the first woman to win consecutive titles at Flushing Meadows since Serena Williams claimed three in a row from 2012 to 2014.

Osaka is the only woman to win at least one major title over the past four seasons, winning the Australian Open in 2019 and 2021, as well as the US Open in 2018 and last year.

ZVEREV BIDS TO BANISH PAINFUL MEMORIES

Alexander Zverev was beaten by Dominic Thiem in his maiden grand slam final in New York last year after the German had been two sets up.

He will not have to face Thiem this time around as the defending champion is sidelined due to injury.

Zverev was the only player to serve 100 or more aces during the tournament last year, firing down 131 but also racking up more double faults (64) than anyone else.

The world number four won his fourth title of the year in Cincinnati last week but Djokovic is undoubtedly the man to beat at Flushing Meadows.

Novak Djokovic has history in his sights as he begins his US Open quest; after three grand slam titles in 2021, a fourth beckons at Flushing Meadows.

Rod Laver was the last man to achieve a sweep of the Australian Open, French Open, Wimbledon and US Open singles in the same year, all the way back in 1969.

Steffi Graf won all four on the women's side in 1988, and it seemed a knock-in that Serena Williams would do likewise in 2015 when she headed to the US Open with three majors already bagged.

But winning any title at that level is never easy, and Williams famously came unstuck when she faced Roberta Vinci in the semi-finals.

Djokovic will be mindful that what seems an inevitability to the outside world remains very much still only a possibility. After his US Open tribulations last year, and a recent jolt at the Olympics, he will know anything can happen.

Here, Stats Perform looks at how Djokovic's situation at Flushing Meadows carries most of the hallmarks of Serena's own position as she headed into the tournament six years ago.

IT'S ALL ABOUT THE SLAMS

It was not always this way, but Djokovic has reached the point in his career when he can choose targets, decide which records he wants to break, and throw everything at those goals.

At the start of the year in Australia, he savoured triumphing at Melbourne Park for a ninth time and pointed to how Roger Federer, Rafael Nadal, Williams and Margaret Court had achieved so much.

"They've made history already," Djokovic said. "They made a tremendous mark in our sport. I'm trying to build that and develop that myself in a very unique, authentic way that is suitable to me.

"Whether I think about winning more slams and breaking records, of course. Of course, I do. And most of my attention and my energy from this day forward, until I retire from tennis, is going to be directed in majors, trying to win more major trophies."

It had very clear echoes of Williams in 2015, also in Australia, setting out her own ambitions for the year and specifically targeting the French Open and Wimbledon.

"Those are the two I really have my eye on, because I would like to do better at those. And I know I can do better," she said.

Williams set her heart and mind on that twin challenge and won both.

"I definitely am not going to play as much this year, and I'm just going to go for everything when I do play," said Williams.

BUILDING UP

When Williams reached New York in August 2015, she had delivered a 48-2 win-loss record for the season, landing each of the majors alongside the Miami Open and the Western and Southern Open. Petra Kvitova in Madrid and Belinda Bencic in Toronto had been the only two players to get the better of the 33-year-old Williams.

Djokovic has a 38-5 record for the year, albeit it has the feel of a more dominant year for the 34-year-old Serbian. Two of those losses came at the Olympics, in a semi-final and bronze medal match, and the other three came in his first three events on clay, losing to Dan Evans in Monte Carlo, Aslan Karatsev in Belgrade and Nadal in Rome.

When it mattered on clay, though, Djokovic majorly turned up in Paris, gutsily beating Lorenzo Musetti from two sets down in the fourth round, ending Nadal's streak of four Roland Garros titles by sinking the Spaniard in the semi-finals, and then leaving Stefanos Tsitsipas devastated in the final, with another fightback after dropping the first two sets.

Wimbledon followed, and Djokovic by then was openly targeting a Golden Slam – each major and the Olympic title.

Much like with Williams and her loss to Bencic in the Toronto semi-finals six years ago, however, Djokovic showed he was fallible as history beckoned. From a set up, he lost to Alexander Zverev at Tokyo 2020, a blow that was compounded by missing out on bronze when Pablo Carreno Busta sprang another shock.

HISTORY CAN BE A FIERCE OPPONENT

Williams and Djokovic have won non-calendar Grand Slams before, winning four in succession spanning two seasons.

Williams first achieved that from the French Open in 2002 to the Australian Open in 2003, and in 2015 she was aiming for five slams in a row at the US Open, having begun her dominant streak at her home grand slam the previous year.

She won the first set of the semi-final against Vinci, the world number 43, but was then second best to the Italian, with Williams saying her conqueror "played literally out of her mind".

But the disappointment was stark, underlined by Williams' terse response to the question of how disappointed she felt by the result.

"I don't want to talk about how disappointing it is for me," she said. "If you have any other questions, I'm open for that."

The four-in-a-row feat has only been performed once by Djokovic, from Wimbledon in 2015 to the French Open in 2016. Had he not been disqualified during the US Open last year for carelessly hitting a ball that struck a line judge, he would most likely currently be on a four-slam streak.

Those who win the first three slams of the year often do complete the set, but there are four instances of singles players falling one short by failing in the year's last major.

Before Williams, the most recent case was Martina Navratilova in 1984, when the imperious left-hander headed to the Australian Open – then played at the end of the year rather than the start – in pursuit of the Grand Slam. She lost to Helena Sukova in the semi-finals, and said: "If I'd have won, I'd have done it all. If I lost I had to start from scratch. Both are hard to cope with."

Navratilova had won 74 consecutive matches until that loss and ended the season with a 78-2 record.

In the men's game, Jack Crawford (1933) and Lew Hoad (1956) also fell short, both losing in finals of the US National Championships, the tournament that became the US Open. Don Budge (1938) and Laver (1962 and 1969) are the only men to have won a calendar Grand Slam in singles.

The weight of expectation is immense for Djokovic as he pursues what would be his crowning glory, not only sealing the Grand Slam but reaching 21 majors, one ahead of Nadal and Federer and into the outright lead in the men's game. The prospect cannot be ignored, and it will be a heavy burden to carry over the coming fortnight.

As Djokovic said on Friday: "I would be lying if I said that’s not something that I’m thinking about or that my attention is not going that way.

"I’m very motivated to play my best tennis. But I have to hit one ball at a time, as they say, try to be in the moment, have a guiding star in a way, a dream to win a slam here."