Juan Martin del Potro will undergo knee surgery for the fourth time but retains hope of playing at the Olympic Games in Tokyo.

Del Potro, who was a career-high world number three in August 2018 and still in the top 10 fewer than two years ago, has not appeared on the ATP Tour since withdrawing from the Queen's Club Championships in 2019.

The 2009 US Open champion had his first procedure after falling at the tournament in London and another followed in January 2020.

The third operation came last August as pain persisted, but the issue still has not been eradicated.

However, Del Potro said in an Instagram post on Monday that the death of his father earlier this year had motivated him to continue pursuing a return to the court.

The 32-year-old, who won bronze for Argentina at the 2012 Olympics and silver four years later, will go under the knife again in Chicago on Tuesday.

"We've tried conservative therapy but the pain is still there," he wrote.

"[Doctor Jorge Chahla] knows I want to play tennis again and be able to play the Olympics, so we agreed that surgery should be done as soon as possible.

"Of course, these last few weeks weren't easy for me. Everything's so hard since my father's passing.

"But also, I feel the strength he sends me from above. I had this day in which I woke up and called the doctor. I knew I had to try again.

"I hope I can overcome this painful situation. I won't stop trying. Of course, your messages and best wishes are always welcomed. Thanks for the love."

Juan Martin del Potro admitted he was struggling in his bid to return from knee surgery as he eyes next year's Olympics.

Del Potro, 32, last played competitively 17 months ago and underwent a third right knee surgery in August.

The 2009 US Open champion is still hoping to return, but admitted it had been challenging.

"I am having a hard time coming back. I still stand by the desire that I have to continue playing," Del Potro told ESPN on Friday.

"The reality is that it is difficult. I'm going to keep fighting as long as I feel like I want to continue."

He added: "Due to the pandemic, the Olympics Games are next year and I'm excited to be there.

"If I have to close my career, I think it would be to give myself an award to represent my country."

A bronze medallist in men's singles at the 2012 Olympics, Del Potro won silver in Rio four years later, and said he hoped to retire on the court.

The Argentinian also took time to remember the great Diego Maradona, who died on Wednesday.

Del Potro recalled his meetings with Maradona during the 2016 Davis Cup final, which he helped Argentina win against Croatia in Zagreb.

"In that Davis Cup final, every night, on my own without anyone knowing, I saw him 10, 15 minutes before going to sleep," he said.

"He did it in private so that he doesn't disarm the team's structure."

Del Potro added: "He sent me a very nice message after winning and I gave him my racquet."

Novak Djokovic celebrates his birthday on Friday, with the world number one showing no signs of slowing down as he turns 33.

The world number one lifted his 17th grand slam title in January with a five-set win over Dominic Thiem.

Five-set sagas have been the domain of Djokovic throughout his career, with Roger Federer, Rafael Nadal, Andy Murray, Stan Wawrinka and Juan Martin del Potro all sharing the court with him for a series of grand slam thrillers that live long in the memory.

Here we look back at a selection of Djokovic's most epic encounters.

2011 US Open Semi-final v Federer ​– Win

Djokovic is renowned for his power to recover from even the most precarious of positions and Federer was on the receiving end of two such Houdini acts in successive years at Flushing Meadows.

Indeed, after saving two match points in a last-four encounter with the Swiss great in 2010, Djokovic repeated the trick en route to a 6-7 4-6 6-3 6-2 7-5 victory after three hours and 51 minutes.

"It's awkward having to explain this loss," Federer said afterwards. "Because I feel like I should be doing the other press conference."

Federer offered little praise for a stunning forehand winner that helped the Serbian save a match point, saying that at that moment Djokovic did not look like a player "who believes much anymore in winning".

He added: "To lose against someone like that, it's very disappointing, because you feel like he was mentally out of it already. Just gets the lucky shot at the end, and off you go."

2012 Australian Open semi-final v Murray – Win

There has arguably been no tournament where Djokovic demonstrated a greater proclivity for endurance than at Melbourne Park in 2012.

His semi-final with Murray, who was weeks into his partnership with coach Ivan Lendl, produced a bewitching prelude of what was to follow in the final.

Murray pushed Djokovic to the limit in a marathon lasting four hours and 50 minutes, fighting back from 5-2 down in the final set of a match in which the ultimate victor battled breathing problems.

Djokovic recovered from surrendering that lead, however, and clinched a 6-3 3-6 6-7 (4-7) 6-1 7-5 victory to set up a final with Rafael Nadal that somehow surpassed the semi-final as the pair etched their name into the record books.

2012 Australian Open final v Nadal ​– Win

With Djokovic needing to produce an exhausting effort to get beyond Murray and Nadal having taken part in his own classic semi-final with Federer, albeit with victory secured in four sets, both would have been forgiven for putting on a final below their usual standards.

They instead did the exact opposite and delivered a showpiece considered by some to be the greatest final ever.

An undulating attritional battle went for five hours and 53 minutes, making it the longest final in grand slam history and the longest Australian Open contest of all time.

Nadal was on his knees as if he had won the tournament when he took the fourth set on a tie-break and was a break up in a fittingly frenetic decider.

However, it was Djokovic who ultimately prevailed at 1:37am (local time) with a 5-7 6-4 6-2 6-7 (5-7) 7-5 triumph that clinched his fifth grand slam.

Djokovic said: "It was obvious on the court for everybody who has watched the match that both of us, physically, we took the last drop of energy that we had from our bodies, we made history tonight and unfortunately there couldn't be two winners."

2012 US Open final v Murray – Loss

Having been the thorn in Murray's side in Melbourne for successive years, also defeating him in the final of the 2011 Australian Open, Djokovic succumbed to the Scot at Flushing Meadows, but only after a Herculean comeback effort.

Murray took the first two sets, the opener won in the longest tie-break (24 minutes) of a men's championship match. Djokovic, though, appeared primed to become the first man since Gaston Gaudio in 2004 to win a slam final after losing the first two sets.

However, Murray was not be denied and dominated the decider to close out a 7-6 (12-10) 7-5 2-6 3-6 6-2 victory, the longest final in US Open history.

Gracious in defeat, Djokovic said of Murray's first slam title: "Definitely happy that he won it. Us four [Federer, Nadal, Djokovic and Murray], we are taking this game to another level. It's really nice to be part of such a strong men's tennis era."

2013 French Open semi-final v Nadal ​– Loss

With Nadal back from a serious knee injury that cost him seven months of his career, the Spaniard returned to peak form at his favourite slam with another absorbing duel with Djokovic.

Lasting four hours and 37 minutes, it did not quite match the heights of their Australian Open opus, but there were enough twists and turns to satisfy those clamouring for another Djokovic-Nadal classic.

Nadal was unable to serve for the match in the fourth set and Djokovic led 4-2 in the fifth, but a decider stretching one hour and 20 minutes went the way of the King of Clay.

"Serving for the match at 6-5 in the fourth, I was serving against the wind, so I knew it was going to be a difficult game," Nadal said after his 6-4 3-6 6-1 6-7 (3-7) 9-7 win.

"I was ready for the fight. In Australia 2012 it was a similar match - today it was me [that won]. That's the great thing about sport."

2013 Wimbledon semi-final v Del Potro – Win

"It was one of the best matches I've been a part of."

Given his travails of 2012, Djokovic's words after his victory over the 2009 US Open champion served as remarkably high praise.

It was a match worthy of such an effusive tribute.

Having twisted his knee earlier in the tournament, Del Potro's contribution to a phenomenal last-four clash served as one of more impressive feats of the Argentinian's career.

Against another opponent, his unrelenting and thunderous groundstrokes would have prevailed, but it was Djokovic's court coverage that proved the difference after four hours and 43 minutes.

Following his 7-5 4-6 7-6 (7-2) 6-7 (6-8) 6-3 victory, Djokovic said of Del Potro: "[He showed] why he's a grand slam champion, why he's right at the top, because every time he's in a tough situation, he comes up with some unbelievable shots."

2015 French Open semi-final v Murray – Win

Two days were needed to separate Djokovic and Murray as the Parisian skies played their part in the semi-final.

A storm halted proceedings on the Friday with Djokovic 2-1 up heading into the fourth set.

Murray appeared to have benefited from the delay as he began Saturday by forcing a decider, but Djokovic was clinical in wrapping up the fifth in comfortable fashion.

He triumphed 6-3 6-3 5-7 5-7 6-1, though a first Roland Garros title would have to wait, however, with Djokovic stunningly defeated by Stan Wawrinka in the final 24 hours later.

2016 US Open final v Wawrinka ​– Loss

Wawrinka would again prove Djokovic's undoing in New York as an astonishing demonstration of shot-making saw the defending champion dethroned.

The Swiss' 18 hours on court ahead of the final were double that of Djokovic, but his toil paid dividends as he bounced back from dropping the first set on a tie-break.

It was a rare occasion where Djokovic ​– battling a blister on his big toe – was rendered powerless in the face of Wawrinka's 46 winners.

Wawrinka came through 6-7 (1-7) 6-4 7-5 6-3 after three hours and 55 minutes, with Djokovic saying: "Congratulations, Stan, to your team as well. This has been absolutely deserved today. You were the more courageous player in the decisive moment and he deserves his title."

2018 Wimbledon semi-final v Nadal - Win

Spread across two days having been made to wait six hours and 36 minutes for Kevin Anderson to outlast John Isner in the other semi-final, Djokovic and Nadal combined to deliver a spectacle eminently more memorable than the meeting of the two big servers.

Djokovic led by two sets to one when play suspended at 11:02 pm (local time), Wimbledon's curfew ending any hopes of a Friday finish.

The prospect of a swift Saturday was soon put to bed for Djokovic as Nadal claimed the fourth. However, Djokovic eventually came through a deciding set among the finest ever contested by the two greats to seal a 6-4 3-6 7-6 (13-11) 3-6 10-8 victory after five hours and 15 minutes.

It marked a first Wimbledon final since 2015 and the start of Djokovic's return to the top of the sport after struggles with injury saw him tumble out of the top 20 in 2018.

Djokovic said: "Speaking from this position right now it makes it even better for me, makes it even more special because I managed to overcome challenges and obstacles, get myself to the finals of a slam." 

2019 French Open semi-final v Thiem ​– Loss

Djokovic was bidding to become the first man to hold all four grand slams at the same time twice but fell foul of Thiem and the French weather.

The last-four meeting began on a Friday but was suspended three times due to wind and rain before organisers cancelled play for the day.

Thiem eventually edged an enthralling affair 2-6 6-3 5-7 7-5 5-7 in four hours and 13 minutes, but Djokovic was quick to direct his ire at tournament officials.

"It [was] one of the worst conditions I have ever been part of," said Djokovic.

"When you're playing in hurricane kind of conditions, it's hard to perform your best."

2019 Wimbledon final v Federer ​– Win

Few would argue Djokovic did not deserve to retain the Wimbledon title. Grinding down Federer remains one of the most arduous tasks in sport, but most would accept this was a final Djokovic was fortunate to win.

An awe-inspiring match, Federer's was a vintage performance, but it was underscored by missed opportunities that will stay with him long after his dazzling career comes to an end.

Federer had a pair of match points at 8-7 in a captivating fifth set. Both were squandered, and few players in the history of tennis have ever been as ruthless at compounding the missed chances of others as Djokovic. 

He duly exercised his flair for punishing profligacy by winning the first ever 12-all tie-break, clinching a fifth Wimbledon crown 7-6 (7-5) 1-6 7-6 (7-4) 4-6 13-12 (7-3) after four hours and 57 minutes.

"If not the most exciting and thrilling finals of my career, in the top two or three and against one of the greatest players of all time," Djokovic said. "As Roger said, we both had our chances. It's quite unreal to be two match points down and come back."

Juan Martin del Potro was "still nervous" as he watched a replay of his US Open final win over Roger Federer in 2009.

The coronavirus pandemic has brought sport to a standstill around the world, with many broadcasters opting to show classic matches from the past.

Del Potro, whose career has been ravaged by injuries, won his only grand slam 11 years ago, beating Federer in a five-setter in New York.

On his Instagram story on Saturday, the Argentinian was watching a replay of his 3-6 7-6 (7-5) 4-6 7-6 (7-4) 6-2 victory.

Del Potro wrote: "[It's] 11 years later and I'm still nervous."

Del Potro, 31, was last in action in mid-2019 before needing surgery on his knee.

The ATP and WTA Tour seasons are suspended until at least July 13, with Wimbledon having been cancelled for the first time since World War II.

Juan Martin del Potro will undergo knee surgery on Monday after a previous operation failed to rid him of pain, leaving the former US Open winner struggling even to walk up stairs.

The injury-blighted Argentinian suffered a fracture of his right kneecap at Queen's Club last June, a repeat of an injury he suffered in Shanghai in October 2018.

He had hoped to return to action before the end of 2019, but initial surgery did not bring results to the extent Del Potro had hoped, and he has not been able to return to the tennis circuit.

A statement from his communication team declared on Sunday that Del Potro, absent from the ongoing Australian Open, would have an operation in Miami.

The statement said 31-year-old Del Potro had taken advice from doctors in Argentina, Europe and the United States, with the majority of verdicts determining "a new intervention" in his right knee was required.

"After analysing the options, Delpo trusted Dr Lee Kaplan to perform the surgery scheduled for Monday, January 27th in Miami," the statement said.

"We hope that this is the definitive solution to eliminate the pain that not only has prevented Delpo from playing tennis, but also making it difficult for him to perform daily activities."

The statement added that pain has endured through Del Potro's attempts to get back on court, preventing him "from running and jumping, and even activities such as walking up stairs".

Del Potro, one of the most popular players with crowds on the men's tour, hoped to have been back in competition by last October.

His camp thanked well-wishers for their patience, as the statement added: "The situation is never easy when it comes to the physique of an athlete and, more importantly, the health of a person."

Juan Martin del Potro will miss the upcoming Australian Open as he continues his recovery following knee surgery.

Del Potro, 31, is yet to return to the ATP Tour since undergoing surgery in June last year in the latest setback of an injury-ravaged career.

The 2009 US Open champion's comeback will not come at Melbourne Park, with his withdrawal from the year's first major confirmed on Saturday.

"Our two-time quarter-finalist Juan Martin del Potro has withdrawn from #AusOpen 2020 as he continues to recover from a knee injury," the tournament announced via its official Twitter account.

"Wishing you all the best with your recovery @delpotrojuan. We hope to see you back in Australia soon."

Del Potro has played just one Australian Open since 2015, reaching the third round two years ago.

He missed three of the four grand slams last year, having looked to be nearing his best again in 2018, when he reached the US Open final, French Open semis and Wimbledon quarters.

The 2020 Australian Open starts on January 20.

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