Federer, Nadal and Djokovic: What comes next for the 'Big 3' in men's tennis?

Has the changing of the guard arrived in men's tennis?

The U.S. Open is around the corner - set to start 30th August 2021 in New York City - and will be without at least one of the sport's "Big 3" players as Roger Federer announced recently that he would undergo another knee surgery and miss the coming months of competition.

What about the chances for Federer's fellow superstars in Rafael Nadal and Novak Djokovic?

Nadal's U.S. Open status remains in limbo after the Spanish great returned home from North America to further treat a lingering left foot injury.

Djokovic, meanwhile, the lone of the three to play at the Olympic Games Tokyo 2020 - where he finished fourth in both singles and mixed doubles - opted to skip big lead-in events in Toronto and Cincinnati for more rest.

Can he contend for the U.S. Open title without a warm-up event? Of course he can, but let's take a closer look at the status of this legendary trio, who are currently locked at 20 majors each - tied for the all-time record in men's tennis.

Novak Djokovic: 'Turning my focus to' NYC

The current world No.1 and undisputed favourite for the U.S. Open, Djokovic had won all three of this year's majors - the Australian Open, French Open and Wimbledon - before hitting turbulence in Tokyo.

Into the semi-finals of both the singles and mixed doubles, Djokovic subsequently lost the next three matches he played - and withdrew from a fourth - meaning he left the Olympics without a medal.

His quest for the "Golden Slam" - all four majors and Olympic gold in one season - had been a talking point in the lead-up to Tokyo, but instead he left the Games with a semi-final loss to Alexander Zverev and a defeat in the bronze medal match to Pablo Carreno Busta.

He did not play the bronze medal match in mixed doubles with partner Nina Stojanovic.

But Djokovic now squarely focussed on one big target: A fourth U.S. Open crown.

"I'm taking a bit longer to recover after quite a taxing journey," he wrote on Twitter. "I'll be turning my focus to the U.S. Open... can't wait to see you in New York!"

Djokovic: Favoured at U.S. Open

A rested and refreshed Djokovic could be dangerous for the rest of the field: Djokovic is particularly hard to beat in the best-of-five-sets format, with a career record of 345-52.

In fact, since the start of 2020, Djokovic has lost just one completed match in the best-of-five format: That was to Nadal at the 2020 French Open, a loss he avenged in this year's semi-final.

While the Serb has "only" won the U.S. Open three times, he's been to the final another five, and three semi-finals, compiling a 75-12 New York record overall.

Simply put: When he steps on the court in Queens, he'll be the favourite among the 128-player field.

Rafael Nadal: Foot injury clouds Open chances

Tennis fans delighted in Nadal, now 35, at a new venue earlier this month, Rafa having taken a wild card into the ATP event in Washington, D.C.

But after a hard-fought win over Jack Sock in his first match since the French Open in early June, Nadal fell to world No.50 Lloyd Harris in the third round and was clearly playing through pain.

Intending to compete the following week in Toronto, Nadal pulled out of the event citing the same foot injury that set him out for both Wimbledon and Tokyo already this year, and then travelled back home to Spain to work with medical staff there to try and be ready for the U.S. Open.

"Today, with this pain, I am not able to enjoy it, and I really don't believe that I have the chance to fight for the things that I really need to fight for," Nadal said, referencing his want to still go after the sport's biggest prizes.

The last time Nadal played the U.S. Open - in 2019 - he triumphed there, his fourth victory in New York.

Prior to D.C. he had played just one event - the Australian Open - on hard courts this year, falling to Stefanos Tsitsipas in the quarter-finals.

Roger Federer: Knee surgery beckons

Federer celebrated his 40th birthday on 8 August by showing his fans he's still got killer hand-eye coordination... at least on the table tennis table.

But a day later, Federer posted a video announcement to his Instagram, sharing that he was set to undergo another knee surgery and would be out for the rest of the 2021 season.

"I will need surgery - so I decided to do it," Federer said, noting that he would be on crutches for "many weeks" and out of the game for "many months."

"It's going to be difficult... but I know it's the right thing to do."

"I want to give myself a glimmer of hope to return to the tour in some shape or form," he added. "I am realistic, don't get me wrong; I know how difficult it is at this age to do another surgery, but I'm going to try it. ... I want to be healthy."

Federer has played sparingly since the beginning of 2020, missing an entire year as he dealt with his knee - undergoing two different surgeries - before returning in February earlier this year.

He made an inspired run to the Wimbledon quarter-finals last month, only to be stopped by world No.18 Hubert Hurkacz in straight sets.

While that puts 2021 on the shelf for Fed, his determination to get back on the court sometime in 2022 is clearly felt.