Alexander Zverev believes world number one Novak Djokovic remains the favourite for the upcoming U.S. Open despite the German backing up his Olympic gold medal with victory in Cincinnati.

The German world number four defeated Andrey Rublev in straight sets on Sunday to win the Western and Southern Open, claiming his fourth title of the ATP season.

The 2021 U.S. Open begins next Monday with Dominic Thiem, who defeated Zverev in the 2020 final, withdrawing from the men's draw along with superstar Roger Federer and Rafael Nadal.

Their absences have opened up an opportunity for the in-form Zverev to have a run at the title but the German insisted Djokovic, who he defeated in the Olympic semi-finals, is the player to beat.

"I do think that he's still the favourite," Zverev told reporters after his win in Cincinnati.

"I do think he's going to be playing incredible tennis there. He's going to be fresh, and I think there is also other guys that are in very good form. I think Rublev is in very good form, [Daniil] Medvedev, [Stefanos] Tsitsipas, all those guys are playing great tennis.

"It's definitely going to be an interesting US Open. But I'm also looking forward to it, because I know where I stand, I know how I'm playing, and I hope I can continue the work and hopefully play even better in New York."

Djokovic has not played since Tokyo 2020, where he lost his bronze medal match to Pablo Carreno Busta after his semi-final defeat to Zverev.

The Serbian world number one opted to withdraw from the mixed doubles' semi-final afterwards, citing a left shoulder injury.

"I think Novak will be back. He's obviously going to be the favourite but I think other guys are going to be in great shape,” Zverev said.

"I'm looking forward to the week. Let's see how it goes. But there is still one week to go. I still have a lot of work ahead of me. I have to find my rhythm in New York, as well."

Zverev, who had never won a match in Cincinnati prior to this year's event, has not lost a match since his Wimbledon fourth-round exit to Felix Auger-Aliassime in July.

World number one Ash Barty says her Western and Southern Open title holds her in "good stead" ahead of the U.S. Open which starts at Flushing Meadows next Monday.

The Australian defeated unheralded Swiss Jil Teichmann in straight sets in Sunday's final in Cincinnati in the perfect preparation for the U.S. Open.

Barty has never gone further than the fourth round at Flushing Meadows and did not compete in last year's U.S. Open due to COVID-19 concerns.

The 2021 Wimbledon champion, who also won the 2019 French Open crown, looms as a strong favourite for the women's singles title although she is typically refusing to get carried away.

"I think we're just excited that we've got matches under our belt in tough conditions here in Cincy, and that's put us in really good stead going into New York," Barty said.

"This week it was completely 'non-result-focused'. It was about preparing in the best way possible, knowing that we wanted to be ready for New York in a couple of weeks' time.

"Now that we've only got a week in between, we have played plenty of matches, and now it's about kind of refining as best we can to hopefully be feeling good come the first round in New York and just try and do the best that we can there."

On her favouritism, she added: "There are no certainties in sport, no certainties in tennis. It's just about playing each and every day as best you can as they come, and not focusing or concerning yourself or your self-worth with results."

Riding the wave of her Wimbledon triumph, Barty crashed out of the women's singles in the first round at Tokyo 2020 to Spaniard Sara Sorribes Tormo last month.

The Australian remained grounded after her Cincinnati victory and insisted preparations for the U.S. Open would stay normal.

"I think sometimes after big wins - and I felt it both times after the French Open and after Wimbledon - there's been a little bit of a big crash, more emotionally than anything else, because there's so much invested into that event," Barty said.

She added: "Our practice weeks before grand slams are quite normal. There is nothing fancy, no extra emphasis on anything.

"It's just gauged by how I'm feeling physically, how I'm feeling mentally, and we have had a lot of practice now as a team in being able to read each other and what we think is required.

"Then it's about going out there for the first round, whether it's the Monday or Tuesday, and try to do the best that I can. That's all I can ask of myself."

The draw for the U.S. Open will be revealed on Friday with Barty going in as the top women's seed, with Aryna Sabalenka second seed and reigning champion Naomi Osaka third.

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 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."

Roger Federer is in the draw for the US Open, but it remains unclear whether he will be fit to take part in the final grand slam of the year.

The United States Tennis Association confirmed on Wednesday that Federer was one of six former men's champions to receive direct entry into the draw.

Federer this month withdrew from the Olympic Games, citing a setback with his knee, on which he had two surgeries in 2020.

The Swiss, though, expressed his desire to return the tour, with Flushing Meadows providing his last chance to add to his tally of 20 major titles in 2021.

A five-time winner in New York, Federer has not reached the final at the US Open since 2015.

In the women's singles draw, Naomi Osaka and Serena Williams have each received direct entries into the draw.

Reigning champion Osaka missed Wimbledon having withdrawn from the French Open after the first round to protect her well-being amid a fallout following her decision to not attend post-match media conferences.

Williams is still awaiting a record-tying 24th grand slam title, the 39-year-old forced to retire from her first-round match at Wimbledon because of an injury to her right leg.

Novak Djokovic has confirmed he will enter the Olympic Games in Tokyo, with the world number one just two titles away from a first men's Golden Slam.

Rivals Rafael Nadal and Roger Federer, citing respective scheduling and injury issues, have each withdrawn from Tokyo 2020.

But Djokovic confirmed on Thursday he will travel to Japan in pursuit of a groundbreaking achievement.

Only women's tour legend Steffi Graf has previously won all four majors and the Olympics in the same year, doing so in 1988.

Doubles superstars Bob and Mike Bryan held all five titles at once but collected them across 2012 and 2013, while Andre Agassi and Nadal are the only two men's singles players to achieve the feat across an entire career.

Djokovic has already triumphed at the Australian Open, French Open and Wimbledon in 2021, leaving Tokyo and the US Open still to conquer.

The 20-time grand slam champion – a record he tied at the All England Club on Sunday – has entered the Games three times previously but earned only a single bronze medal. Andy Murray is the two-time defending champion.

At Flushing Meadows, Djokovic is a three-time winner.

The 34-year-old confirmed his Olympics plans in a social media post as he sent a message to a young Japanese fan celebrating his sixth birthday.

"Cannot disappoint my little friend Koujirou," Djokovic wrote. "I booked my flight for Tokyo and will proudly be joining #TeamSerbia for the Olympics."

He had said following his Wimbledon win last week: "My plan was always to go to Olympic Games, but right now I'm a little bit divided."

Djokovic added limitations on his travelling party and potentially being unable to watch fellow athletes had reduced the likelihood of an appearance to "50-50".

But he will now feature, even if former Wimbledon champion Pat Cash believes the calendar Grand Slam – winning the four majors but not the Olympics – has to be the Serbian's priority.

Cash told Stats Perform: "It's the Olympics, okay – maybe he wants to do that, but certainly his goal is now to try and win all four grand slams in the calendar year.

"He has done four in a row, but he hasn't done them in the same year, which is very, very tough to do.

"There is a reason why I think one person has done it in [men's] professional tennis – Rod Laver and it was in 1969, so it's not easy to do.

"But I really do think it's in his sights and that has got to be his priority.

"It's absolutely the absolute peak of our sport to win all four grand slams in one year."

Roger Federer's body has been saying no for the past two years, but Pat Cash is hopeful the 39-year-old will return for another run on the ATP Tour.

After suffering a setback to his longstanding knee injury during Wimbledon, the 20-time grand slam champion has this week withdrawn from the Tokyo Olympics.

Despite being without much match practice – playing just four tournaments before Wimbledon after coming back from two knee surgeries - Federer was able to make the quarter-finals at All England Club.

However, he suffered a demoralising loss to Hubert Hurkacz in straight sets in the last eight that promoted a fresh round of speculation over his future in the game.

Cash, who won Wimbledon in 1987, hopes Federer will be back despite his recent injury woe.

He told Stats Perform: "First of all, let's hope that Roger Federer will keep going. 

"I think he can, I think he just needs more matches and probably needs to make sure that he's able to last. 

"But your body starts saying no at some stage and it's been saying that for a couple of years now for him." 

Wimbledon winner Novak Djokovic is now level with Rafael Nadal and Federer on 20 slams.

Cash believes judging the Swiss star purely on grand slam titles is not a fair measure of his brilliance, pointing instead to his astonishing record totals of 58 major quarter-final berths and 46 semis.

"He has been the most consistent player that I think we've ever seen," Cash said. "He may not end up with as many grand slams but his consistency is just outrageous.

"All the other players have lost early in grand slams, the Djokovics, the [Andy] Murrays, then the Nadals had lost early in grand slams, Roger just doesn't do it.

"Of all the titles that he's won, I think for me, his most impressive record is how many semi-finals or quarter-finals in grand slams in a row that he got to. It was something ridiculous for 10 or 11 years.

"He never failed at any grand slams and that is just absolutely mind blowing."

However long he tries to play on, Cash insists nothing can sour the memories of an extraordinary career from Federer.

Cash added: "Obviously, he raised the bar as far as the standard of tennis has gone. 

"The other players really had to catch up. Novak admitted it, he said, 'Without Roger there, leading the way, I wouldn't have been as good a player as I could have been'. 

"That's the gold standard of Roger Federer over his career and I'm not sure anybody will be as consistent as him in tennis history. 

"He's just phenomenal the way he plays, and we all of course enjoy the style, his movement. And he's a class act off the court as well."

Federer's status for the US Open, which begins on August 30, is unclear, with Djokovic looking to take the outright lead for major titles and achieve a historic calendar year Grand Slam.

Roger Federer has withdrawn from the Tokyo Olympics because of a setback to his knee suffered during the grass-court season.

Olympic gold in singles is one of the few honours missing from Federer's glittering resume, the 20-time grand slam champion having won silver in 2012, losing the gold medal match to Andy Murray less than a month after beating the Briton in the Wimbledon final.

While Murray will be in Tokyo to attempt to defend his title again having successfully retained it in 2016, Federer – a doubles gold medallist in 2008 – has elected not to make the trip to Japan.

"During the grass-court season, I unfortunately suffered a setback with my knee, and have accepted that I must withdraw from the Tokyo Olympic Games," Federer wrote in a statement on Twitter.

"I am greatly disappointed, as it has been an honour and highlight of my career each time I have represented Switzerland.

"I have already begun rehabilitation in the hopes of returning to the tour later this summer. I wish the entire Swiss team best of luck and I will be rooting hard from afar. As always, Hopp Schwiz!"

Federer missed most of the 2020 season due to persistent right knee problems that led him to undergo two surgeries.

The length of his recovery forced Federer to miss this year's Australian Open but he made his return to the tour in time for the French Open, reaching the fourth round before withdrawing to focus on the grass-court season.

Yet he was stunned by Felix Auger-Aliassime in the second round in Halle and was often unconvincing in progressing to the quarter-finals at Wimbledon, where his quest for a ninth title was ended by Hubert Hurkacz, the Pole becoming the first player to win a set 6-0 against Federer at the All England Club.

The 39-year-old's withdrawal makes him the latest tennis big name to pull out of the Tokyo Games. On the men's side, Rafael Nadal and Dominic Thiem decided against competing, while Serena Williams confirmed before her first-round retirement at Wimbledon that she had no plans to play at the Olympics.

World number one Novak Djokovic has said he is "50-50" on going for his first Olympic title. Having won all three majors so far this year, Djokovic is in prime position to become the first man to do the 'Golden Slam' in the same season. Steffi Graf achieved the feat in 1988, with a sweep of the majors followed by her victory at the Seoul Olympics.