Rafael Nadal described Novak Djokovic's absence from the US Open as "very sad" after the Serbian revealed he would not compete at Flushing Meadows.

Djokovic announced he would not be making the trip to New York on Thursday, due to visitors to the United States being required to display proof of vaccination against COVID-19.

The US Open will represent the second grand slam Djokovic has missed this year, after his unvaccinated status saw him deported from Melbourne ahead of the Australian Open in January.

Nadal is one of the most likely players to benefit from Djokovic's absence as he bids to win a 23rd grand slam title, but the Spaniard expressed sympathy for his rival as he prepared to begin his US Open campaign against Rinky Hijikata next week.

"From my personal perspective, it's very sad news," Nadal said. "It's always a shame when the best players in the world are not able to play a tournament because of injuries or because of different reasons.

"It's tough for the fans, tough for the tournament. In my opinion, tough for the players, too, because we want to have the best field possible."

Nadal's clash with Hijikata will represent his first outing at Flushing Meadows since he beat Daniil Medvedev to win the 2019 title, and injuries have caused him to miss four of the last 10 editions of the tournament.

Roger Federer, another of Nadal's great rivals, will also miss the competition after undergoing three knee operations in two years, but the Spaniard believes the major championships can cope with the absences of tennis' aging stars.

"The world of tennis [will] keep going, even if it is not good news for everyone," he added. "The world continues and the tennis will continue after me, after Novak, after Roger.

"Without a doubt, Novak is one of the most important players of the last 20 years, [in] the history of our sport. In a personal way, I feel sorry for him that he's not able to travel here."

Meanwhile, Federer is hoping to return to the court for September's Laver Cup, where he will join Nadal and Djokovic in a star-studded Team Europe line-up, and the Swiss maestro's old foe is desperate to see him make his long-awaited comeback.

"I'm super excited to see Roger again on court, of course," Nadal said. "I hope he's healthy enough to make that happen.

"It has been a long period of time without Roger on court so I really hope that he can manage to be back.

"The most important thing at this stage of his career is the health and the happiness, no? If he's healthy enough and happy enough to be back on the tennis tour, it will be amazing. 

"If not, we can say thanks to him for everything that he achieved. I am confident that we will keep having Roger for a while."

Nick Kyrgios has announced via social media that he will not be featuring at this year's Laver Cup in London.

The Australian has played in all the previous four editions of the tournament, but has stated he will instead spend time with his family rather than represent Team World at the O2 Arena.

Wimbledon runner-up Kyrgios has not played a singles match since his defeat to Novak Djokovic in the final in SW19 on July 10.

He has been involved in doubles action, however, winning the doubles title at the Atlanta Open with playing partner Thanasi Kokkinakis.

Kyrgios' absence will be a big blow for Team World in London next month, which is due to be captained by John McEnroe.

In an Instagram story, Kyrgios said: "No Laver Cup for me this year!!! Just letting you all know. Gotta have that home time with my family and beautiful girlfriend."

A dream team of Rafael Nadal, Roger Federer and Andy Murray will be complemented by Novak Djokovic at the Laver Cup.

Nadal, Federer and Murray had already been confirmed for the 2022 edition of the tournament, to be held in London in September.

And Djokovic, who won his 21st grand slam title at Wimbledon earlier this month, has now joined his fellow greats to add to a formidable Team Europe line-up.

The Serb last competed in the Laver Cup in 2018, and while it is yet unclear if he will be able to feature at the upcoming US Open due to his COVID-19 vaccination status, Djokovic is relishing the chance to play alongside the best players of the modern era.

He said: "It's the only competition where you can play in a team environment with guys that you're normally competing against and to be joining Rafa, Roger and Andy – three of my biggest all-time rivals – it's going to be a truly unique moment in the history of our sport."

"I don't think I could have imagined having these four icons of the sport on one team together," said Team Europe captain Bjorn Borg.

"I know they, like I, appreciate the significance of this moment and will be truly up for it.

"Each year our goal is to win. With Rafa, Roger, Andy and Novak on the team, I like our chances."

The quartet have accounted for 66 of the last 76 grand slam titles won in men's tennis, while one of them held the number one spot every week between February 2004 and February 2022, when Daniil Medvedev ended that run.

Felix Auger-Aliassime, Taylor Fritz and Diego Schwartzman have been confirmed to be competing Team World - led by John McEnroe.

Six players will compete on each team, meaning Team Europe still have two more spots to fill, while Team World have three spare.

Roger Federer hopes to replicate fellow tennis great Rafael Nadal's "incredibly inspiring" recovery from injury when he makes his own comeback from knee surgery.

Nadal suffered from a recurring foot problem last season but returned to secure a record 21st grand slam title at the Australian Open in January, moving ahead of Federer and Novak Djokovic in the men's all-time list.

Federer has been out of action since losing in the Wimbledon quarter-finals last year, where he sustained another problem with his knee and subsequently underwent a third surgery in the space of 18 months.

The Swiss is yet to put a timeframe on his full ATP Tour return, although he is scheduled to play at the Laver Cup in September before playing the Swiss Indoors Basel event in his home city in October.

Federer, who turns 41 in August, referenced Nadal as he expressed his hopes to emulate the Spaniard's 20-match winning streak that he embarked on when returning from injury this season.

"It's incredibly inspiring when someone comes back from massive health problems," Federer told Caminada Magazin.

"Rafa and I talk on the phone from time to time, we talk a lot. I knew he wasn't doing great, but when he made it I was really happy for him. The effort is immense."

As for Federer's recovery, the world number 46 detailed the struggles he has to go through just to make it onto the court.

"As with a car, you have to turn a thousand screws until the engine runs smoothly," he added. "Today, mobilisation, stretching, and a warm-up in the morning take about 45 minutes. Then we drive to the plant. There follows a warm-up on the pitch, half an hour. 

"After that I eat, stretch, strengthen my ankles with tapes, then warm up again, do gymnastics and explosive speed exercises. Before I finally play, I took care of my body for two and a half hours.

"I don't post many pictures of the strenuous training because I was always convinced that it was a matter of course. Everyone trains hard. 

"I swore to myself that by the end of my career I wouldn't be completely broken. Later I would like to go skiing with the children and play football with my colleagues. That's why I'm doing rehab now – not just for tennis. Also for life after your career."

Asked when he will make his comeback, Federer added: "I can't even think that far. I'm waiting for the doctors' okay. I'm ready to give it my all again. 

"I feel like a racehorse scratching its stall and wanting to race. In the summer I hope to be able to hit the ground running. 

"I'm looking forward to coming home in the evening after the tough day of training and being completely exhausted."

Roger Federer will make his comeback at the Laver Cup in September before playing the Swiss Indoors Basel event in his home city.

It means the legendary 20-time grand slam winner is set to miss all four majors this year.

The eight-time Wimbledon champion will turn 41 in August, and it remains to be seen whether the two events turn out to be farewell tournaments before he retires.

Federer has battled knee trouble over the past two years and has barely featured on the ATP Tour, with his most recent appearance coming at Wimbledon last year, where he was beaten in the quarter-finals by Hubert Hurkacz, a straight-sets defeat that culminated in a 6-0 third set.

The Swiss great has undergone surgery in an effort to finish his career on his own terms.

News of his comeback plans were announced by the Swiss Indoors organisers, who issued a statement that said: "Ten-time singles champion and hometown hero Roger Federer has announced his comeback to the stadium at St Jakobshalle. The Swiss all-time great has confirmed his initial agenda will include the Laver Cup in London followed by the Swiss Indoors in Basel."

Responding to the announcement, Federer posted on Instagram: "Looking forward to playing back home."

The Laver Cup takes place in London from September 23 to 25, and the Swiss Indoors Basel runs from October 24 to 30.

Federer will play his opening match at the latter on Tuesday, October 25, the organisers said.

"The worldwide interest in the return of the hometown hero and 20-time grand slam champion to the ATP Tour is expected to be tremendous," the Swiss Indoors statement added.

Federer for a long time held the record for the most grand slam singles titles won by a man; however, he has been joined on 20 by Novak Djokovic, and Rafael Nadal moved out on his own with 21 by triumphing at the Australian Open this year.

Roger Federer says he hopes to return to action by the end of the summer, with his recovery from knee surgery likely to rule the 20-time grand slam winner out of Wimbledon.

The 40-year-old underwent surgery on his right knee for the third time last August, and has missed five of the last seven grand slams.

Federer made the quarter-finals at Wimbledon last year, but coach Severin Luthi recently said that he "can't imagine" the eight-time Wimbledon winner featuring in London this summer.

Federer has now provided an update on his recovery to Swiss broadcaster SRF, saying that the end of summer or start of autumn is a realistic target for his return, which could mean he is back for the US Open that starts on August 29.

However, he feels "positive" about his return to the court whenever that comes.

"It will certainly be a while," Federer said. "The end of the summer, early autumn, [that's] where I'm aiming for a comeback.

"It's [the knee] fine. Much better. Obviously, I was on crutches for two months, so you have to start from the bottom.

"It [the surgery] was certainly the right thing to do, the knee wasn't right after Wimbledon [last year], so it couldn't go on.

"Currently I'm in three parts. First, the whole rehab, getting back on your feet at the beginning. Then afterwards, learning to walk and building up the whole thing.

"It's only now where I'm at the phase where I can start thinking about my comeback. I had a very good MRI a few weeks ago, which makes me feel very positive."

Federer's tally of 20 career Grand Slam titles was surpassed by Rafael Nadal in January's Australian Open, and the duo are set, fitness permitting, to team up to represent Europe in the Laver Cup, which takes place in September.

The timeline for Federer's recovery also means that he will miss the second slam of 2022, May's French Open at Rolland Garros.

Rafael Nadal and Roger Federer will combine for Team Europe in this year's Laver Cup.

Nadal became the record holder for men's singles grand slam titles on Sunday, as he came from two sets down to beat Daniil Medvedev in the final of the Australian Open.

Federer, who like Novak Djokovic has 20 grand slam titles to his name, has not featured since losing to Hubert Hurkacz in the quarter-finals at Wimbledon last year.

The Swiss star is recovering from a knee injury and chose to sit out the season's first major in Melbourne.

However, injury permitting, the great rivals will team up to represent Team Europe in London in September.

Europe have won the last four editions of the tournament, though neither Nadal nor Federer featured in 2021.

"The Laver Cup is such a unique event and I've loved competing in it," said Nadal, who has played in the competition on two occasions previously.

"I suggested to Roger we should play doubles together in London and he seems keen, so now we just need to persuade our captain Bjorn [Borg].

"Roger has been a huge part of my career, a big rival and also a true friend. To be part of Team Europe together is great and if we're able to possibly share the court one more time as a doubles pairing then this would be a truly special experience for us both at this stage in our careers."

Federer added: "I'm really looking forward to getting back into competition later this year and Laver Cup is very much part of my plan.

"It's no secret that I love the event and I'm super excited to be returning to The O2 and to London, one of the greatest cities in the world.

"Rafa is an incredible person and an inspiration to me and countless others around the world. He messaged me on social media after the Laver Cup in Boston last year suggesting we play doubles in London and I am definitely up for a Laver Cup 'Fedal' comeback!"

Federer and Nadal have only teamed up for a doubles match once before – in the inaugural Laver Cup back in 2017.

They beat American duo Jack Sock and Sam Querrey in three sets.

John McEnroe promised Team World would bounce back after suffering a 14-1 thrashing by Team Europe at the Laver Cup in Boston.

Europe wrapped up a fourth consecutive Laver Cup triumph as Andrey Rublev and Alexander Zverev capped off a dominant performance.

Having won all four matches on Saturday, Europe needed just one more victory to again retain the trophy, preserving their record of having won each edition of the tournament.

That duly arrived as Rublev and Zverev prevailed against Reilly Opelka and Denis Shapovalov in their doubles clash.

They emerged 6-2 6-7 (4-7) 10-3 victors, to spark European celebrations.

Next year's match will be played in London, and Team World captain McEnroe said: "No one wins the Laver Cup, beats us, John McEnroe, five times in a row. You've got to keep going.

"Team Europe is a great team, no question, incredible team. They had good team spirit. We did, as well."

McEnroe, quoted on the Laver Cup website, added: "If you get a couple of different results, we could have put more pressure on them. But we just came up short in four tiebreakers. You win half those, it's totally different story. We gave it our best, but they were just too good."

Zverev reflected on Europe's win, saying: "The score says that it was 14-1, but it could have gone both ways a lot of the time.

"We [did] a lot of hard work for this victory throughout the whole week. The group of this team has been absolutely amazing.

"I think a lot of us came a lot closer together and to be honest I can't wait for London next year."

Team Europe are poised to seal yet more Laver Cup glory after producing another dominant display against Team World, though the focus was on Nick Kyrgios following comments about his long-term future.

Europe swept Saturday's four matches in Boston to stand on the cusp of a fourth consecutive Laver Cup triumph – the defending champions lead 11-1 and require just two more points to clinch the title.

Stefanos Tsitsipas blitzed Team World's Kyrgios 6-3 6-4 at TD Garden, where Olympic Games gold medallist Alexander Zverev beat John Isner 7-6 (7-5) 6-7 (6-8) 10-5 before US Open champion Daniil Medvedev made light work of Denis Shapovalov 6-4 6-0.

Team Europe secured their fourth win of the day in the doubles – Tsitsipas and Andrey Rublev teaming up to defeat Isner and Kyrgios 6-7 (8-10) 6-3 10-4.

After Kyrgios' straight-sets loss to Greece's Tsitsipas, the 26-year-old Australian star casted doubt over his tennis future.

"This is my probably my last Laver Cup," former world number 13 Kyrgios – an Australian Open and Wimbledon quarter-finalist – told reporters post-match. "I don't know how much longer I will be in tennis.

"This is my last event of the year. I will get my body right ahead of the Australian Open.

"My mum is not doing too well with her health. I'd like to go back and see her."

"As long as I'm on the court, I will try and give my best, but I'm not going to lie and say that I'm going to plan to play four or five more years on tour," Kyrgios said. "That's just not me."

Playing for the first time since earning his maiden grand slam trophy at the expense of record-chasing Novak Djokovic at Flushing Meadows, world number two Medvedev suffered no letdown against Shapovalov.

"I played unbelievably, especially [in] the second set," Russia's Medvedev said in his on-court interview. "I didn't know what to expect because after the US Open, I didn't play for a week and a half. Came here, practised as much as I could the past three days, so I didn't hit [that] many balls, but was surprisingly feeling well.

"I wanted to show that also today. [The] first [set] was not easy, the ball was not going as fast as I wanted [and] he was playing really good. And then I just couldn't miss a ball anymore. I'm really happy about [that]."

Team Europe are on track for their fourth consecutive Laver Cup triumph after earning an early 3-1 lead against Team World.

Opening-day honours went to Bjorn Borg's Team Europe at TD Garden in Boston, where the defending champions moved into the box seat thanks to wins for Andrey Rublev, Matteo Berrettini and Casper Ruud in the singles on Friday.

John Isner and Denis Shapovalov managed to get Team World on the board in the evening's final doubles match against Alexander Zverev and Berrettini 4-6 7-6 (7-2) 10-1.

Roger Federer and Rod Laver were in the crowd as Team Europe – headlined by newly crowned US Open champion Daniil Medvedev and consisting of six of the world's top 10 – made a strong start courtesy of Norwegian Ruud, who overcame Reilly Opelka 6-3 7-6 (7-4), improving his career record to 3-0 against the towering American, and beating him in straight sets for the first time.

Italian star Berrettini then overcame Team World's Felix Auger-Aliassime 6-7 (3-7) 7-5 10-8 in the competition's longest match at two hours, 52 minutes.

Berrettini escaped with the second set after facing two break points in the penultimate game before prevailing against the Canadian in a thrilling match tie-break.

"One of the best matches bar none that I've ever seen played, absolutely just enthralling," said captain John McEnroe, whose Team World are eyeing their first Laver Cup trophy.

Rublev rallied past Argentina's Diego Schwartzman, who won the opening set and led 6-2 and 8-5 in the match tie-break before losing 4-6 6-3 11-9.

"Today we are a bit more lucky; Matteo won a tough match against Felix in a super tiebreak, now you saw my match," said Russian star Rublev.

"It was so close; Diego was leading all the super tiebreak, but in the end I find a way to win.

"This happens. This is tennis, this is sport. It’s emotions. Someone has to win, someone has to lose."

On day two, Stefanos Tsitsipas and Zverev headline the day session against Team World's Nick Kyrgios and Isner.

In the evening, Medvedev will meet Shapovalov before Rublev and Tsitsipas team up for a doubles battle with Kyrgios and Isner.

Stefanos Tsitsipas plans to get the COVID-19 vaccine, having previously declared he would only do so if the ATP Tour made it mandatory.

Greek world number three Tsitsipas revealed last month he would not get a jab due to concerns over side effects.

The ATP Tour has persisted in encouraging players to get vaccinated, with Novak Djokovic the most high profile to have stated he was opposed to it, and Tsitsipas has now backtracked on his original stance.

"I will get vaccinated this year," the 23-year-old told Greek outlet Antenna TV. "So I can go to restaurants and shops. I support all those who get vaccinated.

"I am not a doctor; I am a tennis player, so I may not have the most substantiated opinion when it comes to medical issues."

The French Open runner-up was subject to backlash in his homeland following his initial comments on the vaccine, with a series of top figures questioning his thought process.

"The COVID-19 vaccine has not been tested enough because it is new and has some side effects," said Tsitsipas.

"I know some people who've had them. I'm not against it, I just see no reason for someone in my age group to be vaccinated [yet].

"For us young people I think it's good to pass the virus because we'll build immunity.

"I don't see it as something bad. As I said, it isn't obligatory, everyone has freedom to decide for themselves what's right and what's not. At some point we should all do it, I'm not saying the opposite.

"The time will come when we will not be given many options, but until then I want to see a better version of the vaccine that gives us more pluses than minuses."

Tsitsipas is set to play for Team Europe at the Laver Cup this week after missing Greece's Davis Cup tie with Lithuania due to a foot injury.

Nick Kyrgios, John Isner and Reilly Opelka have been named by Team World captain John McEnroe as his final three picks for the Laver Cup.

The trio join Denis Shapovalov, Felix Auger-Aliassime and Diego Schwartzman for the team event which runs from September 24-26 at TD Garden in Boston.

Laver Cup newcomer Opelka rose to a career-high world number 23 ranking en route to his first ATP Masters 1000 final in Toronto and defeated world number three Stefanos Tsitsipas, who will play for Bjorn Borg's Team Europe.

Isner, who has featured for Team World since the inaugural event in 2017, reached the semi-finals in Toronto and claimed his 16th ATP Tour title in Atlanta at the start of August.

He described the Laver Cup as "a highlight of my year", adding: "To be on a team with guys we're normally competing against is so different and so much fun. We come together so well as a group, the chemistry is awesome and it's such a great environment to be part of."

Australian firebrand Kyrgios is a striking inclusion in Team World's roster, while Team Europe will be without their big three: Roger Federer, Rafael Nadal and Novak Djokovic.

Federer and Dominic Thiem were expected to take part in this year's event, though both were forced to withdraw with injuries.

However, Borg's men still boast six of the world's top 11. World number two Daniil Medvedev leads the line-up, with Tsitsipas and Tokyo Olympics gold medallist Alexander Zverev for company.

Casper Ruud, who collected a 14th win in his last 15 completed matches on tour when he beat Opelka on Wednesday, will feature, while Andrey Rublev and Wimbledon finalist Matteo Berrettini complete the six-man team.

Team Europe have landed the title in each of the three editions of the tournament so far, with Prague, Chicago and Geneva having served as hosts.