World number ones Novak Djokovic and Naomi Osaka will seek to defend their titles at the 2019 US Open which serves off today.

While Britain’s Andy Murray who had hip surgery in January has chosen to skip the tournament, Roger Federer and Serena Williams will be again chasing records at the final Grand Slam tournament of the year.

Swiss great Federer, 38, is seeking a record sixth men’s US Open singles title that would also make him the oldest men’s Grand Slam singles champion in the Open era.

Meanwhile, 37-year-old American Williams – whose defeat by Osaka in last year’s final was marred by her angry outbursts at the umpire – is hoping to equal the all-time record of 24 Grand Slam singles titles.

The tournament at Flushing Meadows, where singles winners take home $3,850,000 (£3.17m), features day and night sessions for most of the rounds.

Last year’s women’s final will be remembered for Williams’ outbursts, where she called umpire Carlos Ramos a “thief” and “liar” after he docked her a game before later accusing him of “sexism”.

Organisers are ensuring the pair will not cross paths this year, with Ramos not officiating any matches featuring Williams or her sister Venus.

There are question marks over the fitness of Williams, who has retired or withdrawn from all five of her non-Grand Slam events this year.

The American, who is seeking to equal Margaret Court’s record of 24 Grand Slam singles titles, missed this month’s Cincinnati Masters with the back problem that forced her to pull out of the Rogers Cup final a few days earlier.

She faces a blockbuster first-round match against Russian five-time Grand Slam champion and long-time rival Maria Sharapova, which opens day one’s night session on Arthur Ashe Stadium.

Sharapova has played just six matches since January because of a shoulder injury.

Since returning to tennis after giving birth in September 2017, Williams has reached three Grand Slam finals but has lost in all of them, including July’s Wimbledon defeat by Simona Halep.

World number one Djokovic is the overwhelming favourite to defend his title and win a 17th Grand Slam crown, which would leave him just one behind Rafael Nadal and three behind leader Federer on the all-time list of men’s champions.

The 32-year-old Serb has won four of the past five Grand Slams and said: “I personally have enjoyed lots of success and have been blessed to play well in the US Open.

“I have not lost too many matches in my career playing night sessions and a lot of matches that I get to play in Arthur Ashe are night sessions. I really enjoy the loud atmosphere in there.”

The big three of Federer, Nadal and Djokovic have won the past 11 Grand Slam titles and it is hard to see beyond them once again at Flushing Meadows. Time is, however, increasingly against Federer. The Swiss great turned 38 earlier this month and the most recent of his five US Open titles was 11 years ago.

But having held two championship points against Djokovic at Wimbledon just six weeks ago, he may feel he has some unfinished Grand Slam business.

“The way I played at Wimbledon is going to give me some extra confidence,” Federer said. “This is probably the best I’ve felt in years coming into the US Open, which is encouraging.”

Nadal, meanwhile, has warmed up by defending his Rogers Cup title – the first time he has retained a non-clay title.

The key for the 33-year-old Spanish world number two will be staying fit, having retired from his semi-final in New York a year ago with a knee problem that has caused him problems throughout his career. He withdrew from Cincinnati two weeks ago because of fatigue.

“I hope to be ready for it. For the moment I am feeling well,” said Nadal, who won the title in 2010, 2013 and 2017.

“I think I am playing well and I am practising well. Now I need to push a little bit more and try to start the tournament in a good way.”

Last year’s runner-up Juan Martin del Potro is absent, having re-fractured his kneecap during Queen’s in June.

The question of who can challenge the Big Three always pops up before every Grand Slam and none of the next generation have so far been unable to answer with any conviction.

Germany’s Alexander Zverev and Greek Stefanos Tsitsipas are among the players in their early twenties who are in the top 10 but have lost momentum in their bid to challenge the ‘big three’.

Since beating Djokovic to win the prestigious ATP Finals last November, Zverev has reached just one Grand Slam quarter-final, while Tsitsipas followed up his Australian Open semi-final in January with a first-round exit at Wimbledon.

Russian 23-year-old Daniil Medvedev, who has risen to a career-high number five in the world rankings after his Cincinnati triumph, is the in-form player having reached three successive finals this month and could be one to watch.

Meanwhile, the spotlight will also be on Australian 24-year-old Nick Kyrgios, who oscillates between the talent that won him the Washington title this month and the behaviour that cost him $113,000 (£93,254) in fines less than a fortnight later.