Serena Williams has withdrawn from the US Open after failing to fully recover from a torn hamstring.

The 23-time grand slam champion, who won six of those titles at Flushing Meadows, has not played on the WTA Tour since sustaining the injury at Wimbledon in June.

She skipped last week's Western and Southern Open in the hope of being ready in time for the her home major in New York, but has now taken the decision to pull out of the event.

"After careful consideration and following the advice of my doctors and medical team, I have decided to withdraw from the US Open to allow my body to heal completely from a torn hamstring," Williams posted on her Instagram account on Wednesday.

"New York is one of the most exciting cities in the world and one of my favourite places to play – I'll miss seeing the fans but will be cheering everyone on from afar. Thank you for your continued support and love. I’ll see you soon."

Rafael Nadal has curtailed his 2021 ATP Tour season due to a long-term foot injury but insists he is working towards a return.

Nadal, 35, has played only twice since losing the French Open semi-final to Novak Djokovic in May.

The Spaniard skipped Wimbledon and the Tokyo Olympics and had withdrawn from this week's Western and Southern Open before the US Open.

Nadal will not now compete in the final major of the season either, while great rival Roger Federer is also out for an extended period.

It clears a path for Novak Djokovic – the third man tied on 20 grand slam titles – to win a record-breaking 21st championship at Flushing Meadows while completing a remarkable calendar Grand Slam.

Djokovic could yet have competition again in the years to come, though, as Nadal is not yet calling time on a glittering career.

In making his latest announcement on social media on Friday, Nadal revealed he has been dealing with his injury since 2005 but has not let it halt him yet.

"Hello everyone," he wrote on his Twitter page. "I wanted to inform you that unfortunately I have to end the 2021 season.

"Honestly, I've been suffering a lot more than I should with my foot for a year and I need to take some time.

"After having discussed it with the team and family, this decision has been made and I think it is the way forward to try to recover and recover well.

"It's a year that I've missed things that matter a lot to me, like Wimbledon, like the Olympics, how the US Open is going to be now, like many other events that are also important to me.

"And in view of the fact that during this last year I have not had the ability to train and prepare and compete in the way that I really like to do it, in the end, I come to the conclusion that what I need is time to recover, change a series of things, try to understand what has been the evolution of my foot in recent times.

"It is not a new injury, it is an injury that I have had since 2005 and it has not prevented me from developing my sports career during all these years.

"If it is true that I have had a season where things are not going as they should, as we would all like, it is time to make decisions, seek a slightly different type of treatment to find a solution to this problem or at least improve it in order to continue to have options for the next few years.

"I have the maximum enthusiasm and predisposition to do whatever it takes to recover the best possible form to keep competing for the things that really motivate me and the things that I've done all these years.

"I am convinced that with the recovery of the foot, and obviously a very important daily effort, this can be achieved. I will work as hard as I can to make it happen.

"Thank you in advance for all the support, understanding and all your expressions of affection that are very important and more in difficult times like these.

"I promise you what I am going to do is work hard to try to continue enjoying this sport for a while longer. A big hug to all."

Two-time US Open champion Venus Williams has been given a wildcard entry to participate in this year's tournament.

The 41-year-old American will be making her 23rd appearance at Flushing Meadows and a 15th in a row.

Williams, who has not missed a grand slam since Wimbledon in 2013, is one of eight wild card selections for the women's singles draw.

Former semi-finalist CoCo Vandeweghe and Emma Navarro are joined by teenagers Hailey Baptiste, Ashlyn Krueger, Caty McNally and Katie Volynets.

Storm Sanders has been awarded a reciprocal wild card in agreement with Tennis Australia.

Naomi Osaka will be looking to defend her title in New York, with the main draw scheduled to run from August 30 to September 11.

Defending US Open champion Dominic Thiem will miss this year's tournament with a wrist injury that will rule him out until 2022.

The 27-year-old suffered the setback at the Mallorca Open in June and also withdrew from Wimbledon and the Tokyo Olympics.

World number six Thiem won his maiden grand slam at Flushing Meadows last year with victory over Alexander Zverev in a five-set thriller, but he will not get the chance to defend his title in New York.

"Having spent a week training on court, I still felt pain in my wrist and I knew that it was not 100 per cent," Thiem posted in a statement on his Twitter page on Wednesday.

"I went to see my doctors again and we have decided to follow a conservative treatment, giving the injury more time to recover.

"I'm very disappointed not to be able to defend my US Open title and to miss the rest of the season.

"But I know this is what I have to do. I have a long career ahead of me, so I will only come back once I'm fully recovered and in good shape to compete."

Thiem has a record of nine wins and nine losses this season, with his best result coming at the Madrid Open in May when reaching the semi-finals.

Twenty-time grand slam winner Roger Federer last week pulled out of the US Open, which runs from August 30 until September 12, after undergoing knee surgery.

Roger Federer will not take part in the upcoming US Open after the 20-time grand slam winner announced he is to undergo knee surgery that will rule him out for "many months".

The 40-year-old has not been in action since losing to Hubert Hurkacz in a Wimbledon quarter-final in July and has completed only five events this year.

Federer underwent two operations on his right knee in 2020 and requires another procedure that the legendary Swiss hopes will give him a chance to return to the court.

"I just wanted to give you a bit of an update on what's been going on since Wimbledon," Federer, who won the most recent of his five titles at Flushing Meadows in 2008, posted in a video message on his Instagram page on Sunday.

"As you can imagine, it's not been simple. I've been doing a lot of checks with the doctors as well on my knee, getting all the information as I hurt myself further during the grass-court season and Wimbledon.

"That's just not the way to go forward, so unfortunately they told me for the medium to long term to feel better, I will need surgery. I decided to do it.

"I'll be on crutches for many weeks and also out of the game for many months, so it's going to be difficult of course in some ways.

"But at the same time I know it's the right thing to do because I want to be healthy, I want to be running around later as well again and I want to give myself a glimmer of hope to return to the tour in some shape or form."

Federer, now ranked number nine in the world, missed more than a year of action after first having his knee operated on shortly after the 2020 Australian Open.

"I am realistic, don't get me wrong," he said. "I know how difficult it is at this age right now to do another surgery and try it. 

"But I want to be healthy, I will go through the rehab process I think also with a goal while I'm still active, which I think is going to help me during this long period of time."

Federer added: "Also a big thank you already now for all of your messages that are going to be coming in because you guys are always incredible. 

"You always think of me. Some of you suffer with me. I'll update you as I move along with my rehab. I wish you all the best and I'll check in with you soon."

The US Open in New York begins on August 30, with Dominic Thiem looking to retain his title.

Roger Federer "is a little uncertain" when he will be back in action just over a fortnight before the US Open gets under way.

The 20-time grand slam winner withdrew from both the Canadian Open and Cincinnati Masters this month as he continues to recover from a knee injury.

Federer has not played since losing to Hubert Hurkacz.in a Wimbledon quarter-final in July and has completed only five events this year.

The legendary Swiss, who underwent two operations on his right knee last year, is unsure if he will feature at Flushing Meadows.

He told Swiss newspaper Blick: "I haven't done anything for a long time because of my knee. After Wimbledon, I had to let everything sink in first.

"This week I'll meet my doctors and my team and then we'll see what happens next. At the moment everything is still a little uncertain."

Federer, who celebrated his 40th birthday last Sunday, remains upbeat despite such uncertainty.

He said: "You have to adapt. It has always been like this in my career. Factors change: degree of awareness, successes, experiences, identity and now just that.

"I'm a quiet guy who takes things with a sense of humour. I always see the good in every situation. If it's not good right now, I know it will get better and it could be a lot worse.

"I am doing very well. My family is healthy. I just turned 40 and I'm still active. Who would have thought it? Certainly not me. I am totally at peace with myself and I am sure that there will be a lot more beautiful things to come."

Novak Djokovic drew level with Federer and Rafael Nadal on 20 major singles titles by winning Wimbledon and the world number one will be bidding to complete a calendar Grand Slam in New York.

Novak Djokovic will not play at the Western and Southern Open after a "taxing" run that has brought him to the brink of a calendar Grand Slam.

The world number one's bid for a Golden Slam faltered at the Olympic Games as he lost to Alexander Zverev in the semi-finals in Tokyo.

Djokovic appeared to tire badly and finished fourth in both the men's singles event and the mixed doubles, opting out of the bronze medal match in the latter.

But victories at the Australian Open, French Open and Wimbledon mean 2021 is still on course to be the best year of Djokovic's career.

And the Serbian is taking a little time to prepare himself for the final push at Flushing Meadows, meaning no appearance in Cincinnati next week.

"Dear fans," he wrote on Twitter. "I wanted to share with you that I am taking a bit longer to recover and recuperate after quite a taxing journey from Australia to Tokyo.

"Sadly, that means I won’t be ready to compete in Cincinnati this year, so I'll turn my focus and attention to the US Open and spend some more time with family.

"See you in New York soon!"

Former world number one Andy Murray has been handed a place in the main draw of the US Open after Stanislas Wawrinka pulled out.

Murray, the 2012 champion at Flushing Meadows, reached the second round of the event last year, which was won by Dominic Thiem.

The 34-year-old, who competed in the men's doubles at the Tokyo Olympics, has only played eight Tour-level matches in 2021. He was handed a wildcard for Wimbledon, where he lost in the third round to Denis Shapovalov.

Novak Djokovic is due to lead a strong men's field for the tournament in August, which will be played in front of capacity crowds.

The world number one is seeking to become the first man to win all four major championships in the same year since Rod Laver in 1969.

Rafael Nadal and Roger Federer, who are tied with Djokovic on 20 grand slam singles titles, are also set to play.

Wawrinka, himself a champion in New York in 2016, is still recovering from his second foot surgery of the year.

Roger Federer turned 40 on Sunday amid uncertainty over whether he will grace the stage of a grand slam again.

Both he and Serena Williams, who reaches the same birthday landmark in September, have kept their future plans under wraps.

However, it would come as no surprise now if one, or both, were to retire by the end of the year.

Injuries are taking their toll, and even the greatest champions cannot go on forever.

Stats Perform looked at both Federer and Williams, considering what they may still want to achieve, and their prospects of attaining those remaining goals.

Federer's final fling?

Ahead of his 30th birthday, Federer was asked what it felt like to hit such a milestone.

"Birthdays happen. They're part of life," Federer said. "I'm happy I'm getting older. I'd rather be 30 than 20, to be honest. To me it's a nice time."

A decade on, Federer has good reason to be satisfied with life as he chalks up another decade. Family life is good, he'll never need to borrow a dollar, and he has advanced from 16 grand slams to 20.

But the knees would sooner be 30 than 40, and Federer, remarkable sportsman though he is, looks to have entered the lap of honour stage of his career – if he can even complete such a lap.

Two knee operations in 2020 were followed by a setback that ruled him out of the Olympics and will also keep him sidelined for the Toronto and Cincinnati tournaments before the US Open.

Will Federer make it to Flushing Meadows, where he won five successive titles at the height of his career? There has to be doubt over that, and should he indeed be an absentee in New York, what is there left to target? The Laver Cup, perhaps, a tournament in which he is financially invested and which is due to be played in Boston in late September.

Would he play on in 2022? Could he tolerate more long road trips without his family, living in a tennis bubble?

Target: Federer has never settled for second best, and it may have dawned on him at Wimbledon that in all probability he no longer can win a grand slam. Losing a 6-0 set to Hubert Hurkacz on the way to a quarter-final exit would have hurt. The hunger does not go away after 20 grand slams, but Federer's battle-weary body is sending him messages. He will want to go out on his own terms, which means getting fully fit.

Prospects: Assuming the knee issue is not a major problem, and more of a niggle, then Federer could still play the US Open, Laver Cup, Indian Wells and Paris Masters this year. If the mind is willing but the body does not comply, however, then it would not be a shock to see him call time before the Australian Open comes around in January.

Serena still one short of Court

From precocious teenager to queen of the tour, Williams' tennis journey has been a 25-year odyssey and there is nobody more driven to succeed than the great American.

It is an intense frustration that she remains rooted on 23 grand slams, one short of Margaret Court's record haul, and the four grand slam final losses she has suffered while on that mark have been cruel blows.

As her 40th birthday approaches on September 26, prospects of matching Court are fading. The leg injury that cruelly forced her out of Wimbledon in the first round was a harrowing turn of events, given she looked primed to be a big title challenger in London.

She is becoming less of a factor when looking at title favourites, but Williams is still capable of beating top players, still a threat wherever she shows up. It comes down to whether the body lets her chase her goals, and whether the pain of so many near-misses in recent years persuades this great champion the exertion is no longer worth prolonging.

Target: The 24th slam has been the must-have for Williams. Tour titles feel like an irrelevance, and Williams has won just one of those since January 2017, her calendar built around peaking for the majors since returning from giving birth to daughter Olympia.

Prospects: Beating Aryna Sabalenka and Simona Halep at the Australian Open demonstrated Williams still has the game for the big stage, and a semi-final defeat to Naomi Osaka, to whom she has now lost in three of four encounters, should not particularly detract from that. Wimbledon felt like a golden opportunity, with a host of major rivals absent and others struggling for form. There is no doubt she felt that way. Getting to 24 – and beyond – has shifted from feeling like an inevitability to being an odds-against chance now.

Novak Djokovic led the ATP Tour's birthday message to Roger Federer, as the Swiss star celebrated his 40th on Sunday.

Federer, ranked ninth in the world, made his professional debut in 1998. He has gone on to win 20 grand slam titles, a feat matched by only Rafael Nadal and Djokovic, who tied his rivals with his triumph at Wimbledon in July.

His first grand slam title arrived at Wimbledon in 2003, when Federer was aged just 21. In 2004, 2006 and 2007, he won three out of the four majors on offer.

Federer has six Australian Open titles, eight Wimbledon triumphs, five US Open wins and one French Open success to his name, while he has also won six ATP Tour Finals.

Djokovic and Federer have met 50 times on the ATP circuit, with the Serbian shading their head-to-head record with 27 wins – their most recent encounter coming in the semi-finals of the 2020 Australian Open.

Yet it was he who led the tributes to a true great.

"Hey Roger, happy 40th birthday – 40th, wow, what a milestone! You still keep on inspiring and thriving on the court, off the court, inspiring all of us," Djokovic said in a video posted to the ATP Tour's official Twitter account.

"It's been a huge honour to share the tennis court and the tennis circuit with you in the last 15 years.

"Hopefully you can still keep on playing. The sport needs you, of course, and thanks for everything you have done and thanks for showing us that even at that age we can play at a very high level.

"All the best, I wish you health and love and happiness with your close ones and thanks again for everything."

Kei Nishikori, who has beaten Federer three times and suffered eight defeats to the Swiss, was next up.

"Roger, happy 40th birthday!" Nishikori said.

"You are still my idol, I always looked up to you and I hope we can play a couple more times and I hope you can still keep going and win grand slams."

World number 15 Felix Auger Aliassime shares his birthday with Federer, though the Canadian is some 19 years junior.

"Hey Roger, the big 40, while I'm just turning 21," he said. "It's amazing for the sport that I'm playing and you're still playing at the same time.

"I hope I'll still be playing when I'm 40 as well. Thank you for everything you've been doing for tennis, it's so good to still have you around, I hope you have a great birthday."

Novak Djokovic blamed mental and physical exhaustion after another desperate day for the Serbian at the Olympic Games meant he will leave Tokyo empty-handed.

The world number one lost 6-4 6-7 (6-8) 6-3 to Pablo Carreno Busta in the singles bronze medal match, smashing one racket against a net post and tossing another into the stands in gestures of frustration.

Djokovic then cited a shoulder injury as he pulled out of the mixed doubles third-place match. That decision meant Ash Barty and John Peers of Australia took bronze, with Djokovic and his unfortunate Serbia partner Nina Stojanovic finishing fourth.

"I am dealing with injuries. Not one, more than one," Djokovic said in an interview with Serbian media, according to tennismajors.com. "I hope that it won't stop me from going to the US Open, which is my next big goal.

"I feel bad for Nina because we did not fight for a medal in mixed, but my body said 'enough'. I have played under medications and abnormal pain and exhaustion."

The 34-year-old Djokovic said he had put his "very last source of energy" into the tournament and was satisfied with his effort, with a semi-final defeat to Alexander Zverev on Friday having left him resigned to a battle for what by his standards was perceived as a consolation prize.

But Djokovic added: "I know I've not played well today, and yesterday in the second and third set.

"The exhaustion, both physical and mental, got to me and it's unfortunate that in the most important matches I just didn't deliver, but I gave it all."

Djokovic suggested the Paris Olympics in 2024 were a possible target, although he must be becoming sick of Olympic tennis by now, having only one bronze to show for four attempts to win gold.

He took bronze in 2008 but lost to Argentina's Juan Martin del Potro both in the third-place match at London 2012 and the first round at Rio 2016.

Now there is more Games agony to digest, as well as a need to reboot ahead of the upcoming North American hardcourt swing and that US Open campaign. His hopes of a calendar Golden Slam are over but a sweep of the grand slams remains a possibility, having already landed the Australian Open, French Open and Wimbledon titles.

"I've had some heart-breaking losses at the Olympics Games," Djokovic said. "I know that those losses have usually made me stronger. I know that I will bounce back. I will try to keep going for the Paris Olympic Games. I will fight for my country to win medals."

Carreno Busta's reaction was thoroughly refreshing, with the Spaniard jubilant to secure a medal.

He said: "This week has been a very harsh week mentally for me. When I saw Novak lost, and I had to play him for this medal, I had my doubts.

"But last night I slept like I haven't slept in Tokyo. I slept for nine hours straight, that was an advantage to me. I came on to the court today knowing Spain was behind me.

"This is even more incredible than winning other tournaments. I've won Davis Cup, I've gone far in other tournaments, but winning an Olympic medal is indescribable. Words fail me, I felt Spain rallying behind me. A bronze medal is a dream come true for me."

The knock-on effort of Djokovic's withdrawal from the mixed doubles meant Barty and Peers added to Australia's medals haul without having to step on court for the third-place play-off.

Barty insisted she and Peers were worthy bronze medallists, saying: "It's incredible. It's unique circumstances and heartbreaking for Team Serbia not to get out on court.

"But for Johnny and I this is a dream come true for us. I feel like we've really deserved this one."

Novak Djokovic smashed one racket and threw another into the stands on the way to losing his bronze medal match at the Tokyo Olympics on Saturday.

Spain's Pablo Carreno Busta beat the world number one 6-4 6-7 (6-8) 6-3 to finish third in men's singles.

The shock result followed a day on from Djokovic's hopes of a Golden Slam being crushed by defeat to Alexander Zverev in the semi-finals.

In the wake of his singles third-place match setback, Djokovic also pulled out of the mixed doubles bronze match, citing a left shoulder injury.

Having already clinched the Australian Open, French Open and Wimbledon titles, Djokovic was eyeing gold at the Games before heading to the US Open in August, aiming to land the five biggest prizes in tennis in the same season.

That has never been achieved in a calendar year by a man, and Djokovic could not even manage a consolation prize from his singles mission in Japan. How serious his injury is now remains to be seen.

After levelling the singles match by taking the second-set tie-break, Djokovic boiled over in the first game of the decider, firstly when flinging his racket several rows back from the middle of the court after Carreno Busta put away a volley at the net.

Djokovic picked another racket from his bag but petulantly demolished that against a net post after dropping the third game to slide 3-0 behind, receiving a warning from the umpire for that violent outburst.

His anger may have been explained by injury or by his disappointment on Friday, when, as well as losing to Zverev, Djokovic and Serbian team-mate Nina Stojanovic were beaten in the semi-finals of the mixed doubles.

Djokovic would have had one final shot at a medal from his Tokyo trip to come later on Saturday, with the 34-year-old and Stojanovic due to face Ash Barty and John Peers in another match for bronze.

However, shortly after his singles exit, it was announced that Djokovic had pulled out of that match, handing Barty and Peers the medal.

Amid the anger and frustration exhibited on court by Djokovic, it was a banner day for Carreno Busta, as Spain celebrated another tennis medal, having won at least one in eight of the last nine Olympics.

The 30-year-old fell to the court in joy at the end of the two hours and 47 minutes it took him to defeat the world number one, his elation a sharp contrast to the emotions of his beaten opponent.

Alexander Zverev apologised to Novak Djokovic after ending the Serbian superstar's hopes of a glorious Golden Slam – but joked it was about time someone else landed a major tennis title.

In their Olympic Games semi-final, it seemed Djokovic was cruising through to the gold medal match when he surged a set and a break of serve ahead.

Incredibly, though, Zverev won 10 of 11 games from 3-2 behind in the second set to take the match 1-6 6-3 6-1 and set up a shot at Karen Khachanov in Sunday's final.

Djokovic swept to Australian Open, French Open and Wimbledon trophy success before heading to Japan for the Olympics, the fourth leg of a potential sweep of each of the year's majors and the Tokyo 2020 singles title.

He had spoken of it becoming closer to a reality, as he attempted to match Steffi Graf's achievement from 1988, when she followed triumphs at each of the slams by winning in the October 1 final at the Olympics, held in Seoul that year. Graf remains the only player to have pulled off the feat in the same year.

Zverev had other ideas, but he also had sympathy for Djokovic when they exchanged words at the net.

"I told him that he's the greatest of all time, and he will be," Zverev said.

"I know that he was chasing history, chasing the Golden Slam and chasing the Olympics, but in these kind of moments me and Novak are very close. Of course I'm happy that I've won, but at the end of the day I know how Novak feels.

"I feel sorry for Novak, but he's won 20 grand slams, 550 Masters Series or whatever, you can't have everything.

"He's the greatest player of all time, he will win the most grand slams out of anybody on tour, but I'm also happy that I'm in the final."

Victory at Wimbledon earlier in July took 34-year-old Djokovic to 20 grand slam titles, level with Roger Federer and Rafael Nadal for the most by a man in the history of tennis, and Zverev was lurching towards becoming his latest victim when their Tokyo tussle began in a one-sided manner.

"I was down a set and a break, so I needed to change something. I started playing much more aggressive," Zverev said. "I started to swing through the ball a little bit more, and I tried to dominate that way."

Zverev is assured of at least a silver medal now, while Djokovic faces a bronze medal play-off against Spain's Pablo Carreno Busta.

"It's an amazing feeling knowing that you're going to bring the medal back to your house, back home to Germany," Zverev said.

"It's incredible beating the best player in the world undoubtedly right now and in this season. It seemed it was impossible to beat him at this event, so I’m very happy right now. But yet there's still one match to go."

Novak Djokovic has been burned by high expectations at the Olympics before, so it was little surprise that he should express only guarded optimism on the eve of the Tokyo Games.

The Serbian, who has won the Australian Open, French Open and Wimbledon already in 2021, is chasing the gold medal that would leave him one step away from the first tennis calendar 'Golden Slam' by a man.

Should he triumph in Japan over the next fortnight, Djokovic will head to the US Open in late August needing to win in New York to complete the full set.

Steffi Graf, who in 1988 won all the slams and gold at the Seoul Olympics, is the only player in tennis history to have completed such a sensational season.

Djokovic said such a feat was becoming a "more and more realistic" target, as he spoke in a Serbia team news conference, but the last time he stepped off the singles court at an Olympic Games, he was in tears, having lost in the first round at Rio to Juan Martin del Potro.

There is no danger of Djokovic running into his Olympic nemesis in Tokyo, with Del Potro, who also beat Djokovic in a bronze-medal match at the London 2012 Olympics, not a part of Argentina's squad as he battles back from four knee operations.

Looking at his own prospects for Tokyo and the rest of the year, Djokovic said: "It is still a long way to go ... I put myself in a very good position. But I will take things very slowly and cautiously.

"It's an approach I need to have because in the past I wasn't probably fully experienced in that approach. And I started to feel there were a lot of distractions around that influenced my performance.

"I know there are a lot of things on the line, a lot of history on the line. I'm privileged to be in this position. I worked very hard to be here, with my team, of course. But let's talk about history if everything goes great."

After his singles loss in Rio, Djokovic and Nenad Zimonjic lost in the second round of doubles to Brazilians Bruno Soares and Marcelo Melo.

A bronze from Beijing 2008 is all Djokovic has to show for his Olympics career to date, but he is a hot favourite for the title in Tokyo, where he will start against Bolivia's world number 139 Hugo Dellien.

The 34-year-old Djokovic said he "would be delighted to ask" Graf how she achieved her 1988 clean sweep.

"When I was thinking about her ultimate achievement ... I did not think it... I don't want to say 'achievable', but [I thought] there was a slim chance that someone could make it again, both male and female," Djokovic said.

"But right now it seems more and more realistic. Of course, it is one of my goals and dreams."

Djokovic has neither Roger Federer nor Rafael Nadal as rivals in Tokyo, with Federer missing after reporting a knee injury setback and Nadal electing to give the event a miss.

The 'Big Three' each have 20 grand slam titles now, following Djokovic's hot streak, and the Serbian admits it is unusual for both superstars to be absent.

"I have not experienced too many big tournaments in the past 15 years without Roger and Rafa playing. So it's a little bit strange," Djokovic said. "I'm used to seeing at least one of them. But still, some of the best players in the world are here.

"The guys who are in the top six, seven in the world, they are the biggest competitors or candidates for winning a medal. But potentially I am meeting with them in the later rounds."

After winning Wimbledon for a sixth time, Djokovic surprised many by claiming he could skip the Olympics, but he was reeled in by the appeal of representing his country, perhaps for the final time in the Games.

"Without the key element of any sports events – the crowds, the fans, that energy – it's different, but it is still the Olympic Games," he said.

"I was in a dilemma for a little bit, but I decided to come, and I'm glad because there are many more things that are beautiful about the Olympic Games. So I will try to focus on those things."

Ash Barty and home favourite Naomi Osaka start their respective quests for Olympic gold against Sara Sorribes Tormo and Zheng Saisai, while Novak Djokovic opens against Hugo Dellien.

In a stacked women's draw, world number one and Wimbledon champion Barty has a tough opening assignment and could face French Open finalist Anastasia Pavlyuchenkova, the 13th seed, as early as round three.

Spectators may not be in attendance at Tokyo venues for the Olympics but Japanese fans will be rooting for Osaka, who returns to action after a two-month hiatus with the four-time grand slam winner having spoken openly about mental health and anxiety issues.

Viktorija Golubic or Maria Camila Osorio Serrano would await Osaka if she can get through round one, but a dream final with Barty is no shoo-in given 15 of the world's top 20 on the WTA Tour are in action including each of the nine leading the race for the 2021 WTA Finals.

Aryna Sabalenka (3), Elina Svitolina (4), Wimbledon runner-up Karolina Pliskova (5), Iga Swiatek (6) and Garbine Muguruza are all featuring in Tokyo.

The men's side has been hit by a spate of withdrawals, with Rafael Nadal, Roger Federer and Dominic Thiem among those not playing in the Japanese capital.

The main talking point surrounds whether the all-conquering Djokovic can continue his march towards a calendar Golden Slam – a sweep of all four majors and an Olympic gold in the same year.

Any notion of a free ride for the Serbian is wide of the mark, though. His side of the draw could see him come up against Andrey Rublev (5), Alexander Zverev (4) and Hubert Hurkacz (7), while Stefano Tsitsipas (3) – beaten by Djokovic in the French Open final – and Daniil Medvedev (2) are among the potential final opponents.

Andy Murray, gold medal winner in 2012 and 2016, faces Canada's Felix Auger-Aliassime in a tricky first-round match.