The US Open becomes the first Grand Slam of the COVID-19 era when it starts on Monday in a spectator-free bubble at Flushing Meadows following a troubled build-up that saw several top stars withdraw over coronavirus fears.

Novak Djokovic and Serena Williams headline a tournament that will be unrecognisable from previous Slams due to strict safety protocols that were still not enough to convince some of tennis’s biggest names to travel to New York.

Djokovic rallied to defeat Canada’s Milos Raonic 1-6, 6-3, 6-4 in Saturday’s ATP Western & Southern Open final, remaining unbeaten this year ahead of his first US Open match.

The 33-year-old won his 80th career title, improving to 23-0 in 2020 and 11-0 all-time against Raonic, while capturing his 35th ATP Masters Series crown, matching Rafael Nadal’s all-time record.

The victory gives Djokovic a double career sweep of all nine ATP Masters Series titles while Raonic has gone winless in 63 Masters Series starts.

Defending champion Nadal and women’s number one Ashleigh Barty are among high-profile absentees at the US National Tennis Center, which just months ago was transformed into an emergency coronavirus field hospital.

Raucous crowds are a hallmark of the US Open, but this the cavernous Arthur Ashe Stadium will be eerily empty to mitigate the risk of infection from the deadly pandemic that has wiped out much of the tennis season, including Wimbledon.

The players are being kept in a tightly controlled environment with regular COVID-19 testing throughout the tournament. Any competitor who tests positive once the event has started will be automatically withdrawn.

Most competitors are staying at one of two hotels where they will be shuttled the 30 minutes to and from the tennis center.

A few, including Djokovic and Williams, have chosen to stay in private homes where they must pay for 24-hour security approved by the United States Tennis Association (USTA).

The security teams are obliged to provide the USTA with information regarding when the player leaves and arrives at the house.

No player is allowed to travel anywhere other than between the tennis center and their accommodation. Any player who leaves the bubble without the written consent of organizers will be thrown out of the tournament. There will be no lines officials on the outer courts, where Hawk-Eye technology will make line calls.

Organizers are limiting the locker rooms to 30 players at one time, with competitors encouraged to shower and then head outside as quickly as possible where activities including basketball hoops have been put up.

Briton Andy Murray, the 2012 US Open champion, said the atmosphere felt “pretty sad,” but he praised the precautionary measures.

“It feels safe and I’m happy I decided to come,” he told reporters in an online press conference.

The absence of world number two Nadal due to coronavirus concerns and Swiss legend Roger Federer, who is recovering from knee surgery, hands Djokovic a golden chance to close the gap on his fierce rivals in the records race.

Djokovic has captured five of the past seven men’s singles Slam crowns and is overwhelming favorite to capture a fourth US Open title in September 13’s final.

A win on the hard courts would take the 33-year-old to 18 Grand Slam titles, behind Nadal on 19 and Federer on 20.

A depleted women’s field hands Williams a gilt-edged opportunity for a 24th career Grand Slam title to match Margaret Court’s all-time record.

World number two Simona Halep is missing, as is reigning US Open champion Bianca Andreescu of Canada and top ten players Elina Svitolina, Kiki Bertens and Belinda Bencic.

Williams, 38, has a tricky draw though. She could meet 2017 US Open champion Sloane Stephens in the third round, Australian Open champion Sofia Kenin in the semi-finals and potentially Czech top seed Karolina Pliskova in the final.

For Williams, who lost in the US Open and Wimbledon finals each of the past two years, a diminished field doesn’t devalue the title.

“It still has to be tennis that’s played, asterisks or not. I think this whole year deserves an asterisk because it’s such a special year,” she said.

France’s Benoit Paire has tested positive for COVID-19 and will have to pull out of the US Open, French sports daily L’Equipe here reported on Sunday.

Agencies