World number two Alexander Zverev has withdrawn from the US Open as he recovers from ankle surgery.

The German went under the knife after tearing all three of the lateral ligaments in his right ankle during his French Open semi-final against Rafael Nadal.

Zverev will not make his comeback at the final grand slam of the year in New York, as his withdrawal was announced on Monday.

The 25-year-old reached his only major final at Flushing Meadows two years ago, losing to Dominic Thiem.

Zverev stated after his operation that surgery was "the best choice" to ensure his ligaments heal properly and he could return to competition "as quickly as possible."

The US Open gets under way next Monday, with doubts remaining over whether Novak Djokovic will be able to play due to the 21-time grand slam champion opting against receiving a coronavirus vaccine.

Roger Federer looks bang on course to launch his comeback next month after the 20-time grand slam winner posted an encouraging video of a practice session on Sunday.

The Swiss turned 41 on August 8 and has not played a match since losing to Hubert Hurkacz in the quarter-finals at Wimbledon last year.

He has undergone knee surgery in the meantime, his third such operation inside two years, but is determined to resume his playing career and looked to be enjoying being back on court in a short clip posted to Instagram.

Federer is due to play in the Laver Cup, which will be staged in London from September 23 to 25, with Rafael Nadal, Andy Murray and Novak Djokovic set to join him in an illustrious Team Europe line-up.

It will be a reunion for the 'Big Four', who were once so dominant as a group, with Stefanos Tsitsipas and Casper Ruud also on the European team, which will be captained by Bjorn Borg.

Federer is then entered for the Swiss Indoors in his home city of Basel, where he has been champion 10 times previously and holds a remarkable 75-9 win-loss career record.

It remains to be seen whether that October 24-30 tournament is a farewell appearance, or another step towards playing regularly on the ATP tour once more.

At Wimbledon in July, Federer appeared at a parade of former champions and said he wished to play at the All England Club again, which points to him planning to play in the 2023 season.

"I hope I can come back here one more time," said Federer, an eight-time Wimbledon champion.

The prize pot for this year's US Open will top $60million for the first time in the competition's history, event organisers have announced.

The 2022 edition at Flushing Meadows gets under way on August 29 and runs for just under two weeks.

It was revealed on Thursday that $60m will be up for grabs, topping the previous record of $57.5m from last year, with both singles champions to receive $2.6m.

Players will be given $80,000 for making the main draw and $121,000 should they make it to the second round. Runners-up in the singles will pocket $1.3m.

In the doubles, the champions will receive $688,000, the runners-up $344,000 and the semi-finalists $172,000.

Taylor Fritz believes there would be no "harm" in Novak Djokovic competing at the US Open, although the American admits he is conflicted about whether he should be allowed.

Wimbledon champion Djokovic has his route to Flushing Meadows blocked by red tape at present, with the United States refusing to allow unvaccinated foreign visitors to enter the country.

US tennis authorities have pledged to adhere to government rulings surrounding COVID-19 protocols, despite including Djokovic on their entry list.

For Djokovic to be allowed into the United States, it appears he would require a change of policy from law-makers, or he would have to be considered suitable for an exemption.

Among those who would be eligible for such an exemption are "persons whose entry would be in the national interest".

With 21 grand slam titles, Djokovic sits second on the men's all-time list behind Rafael Nadal, who has 22 victories at the majors. 

And Fritz, ranked 13th in the world, said that while the situation is complicated, there is part of him that thinks Djokovic should be allowed to take part in the competition that starts in under a fortnight.

"It's tough," he said. "I think on one side of it, I think it's tough to make certain exceptions to the rules for certain people.

"I don't know how I feel about that, but then, at the same time, we're not the most COVID-safe country in general with how we are doing things.

"So it does seem like, what's the harm of letting the best player in the world come play the US Open?

"But like I said, at the same time, it's conflicting, because I don't know how I feel about making special exceptions just for one person because of who they are.

"So I see both sides of the argument, to be honest. It's tough to differentiate, obviously. It's good for every player if Novak is not in the draw."

Pablo Carreno-Busta came back from a set down to mount a superb comeback against Hubert Hurkacz and win the first ATP 1000 event of his career on Sunday.

The Spaniard became the first unseeded player to win the tournament since Guilhermo Canas in 2002 after weathering an early storm to shock the eighth seed 3-6 6-3 6-3 in Montreal.

Having come through a gruelling semi-final encounter with Dan Evans to reach his first ATP 1000 final in singles, the Tokyo 2020 bronze medallist struggled to deal with his opponent's impressive slew of aces in the first set, and saw his serve broken in the sixth game.

But a ruthless start to the second set saw Carreno-Busta break early, racing out to a 3-0 lead and holding his nerve to keep the gap to his Polish opponent, who was chasing a second ATP 1000 crown.

World number 10 Hurkacz attempted to rally with a fine start to the third set, but another loss of serve effectively stalled his momentum and Carreno-Busta was able to take the victory.

The result marks a much-needed boost for Carreno-Busta, who suffered first-round exits at the French Open and Wimbledon after making the last-16 in Australia, with the U.S. Open set to start later this month.