Time is running out for Kei Nishikori and his quest to play in the US Open after the Japanese star revealed he had again tested positive for coronavirus.
Nishikori's hopes of playing at the New York grand slam have faded further after the Japanese former world No.4 confirmed that he was still not free of the virus.
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The 30-year-old, a finalist at Flushing Meadows in 2014, withdrew from the Western & Southern Open hardcourt warm-up after his first positive test last week.
"Just a little update, I just took another COVID test and am still positive. I have very minimal symptoms and am staying in full isolation in Florida," Nishikori posted on social media late on Friday.
"The next test will be early next week at which time we will update you with more information."
Nishikori will need to return two negative tests in order to enter the bubble in New York, with the US Open getting underway on Monday week (AEST).
The Japanese star, who has been staying at the IMG Academy in Florida, has enjoyed his greatest grand slam success at the US Open, reaching the semi-finals in 2016 and 2018 in addition to his loss to Marin Cilic in the 2014 title decider.
The US Open starts on August 31 in New York but a string of top players have withdrawn over fears of contracting coronavirus, which has infected more than 5.6 million people and killed 175,397 in the United States.
Defending champions Rafael Nadal and Bianca Andreescu as well as Australian women's world No.1 Ashleigh Barty are among those who have decided not to travel to New York.
Big-name absentees present Djokovic with huge opportunity
Roger Federer is also missing from the event because of injury, leaving Novak Djokovic with a golden chance to snare his 18th major title.
The World No.1 has come under fire after confirming that he's renting a New York house, rather than staying in the quarantine bubble set up for other players.
The Serbian felt the hotels would be too suffocating and he battled with organisers to be allowed to stay elsewhere - even though he has had to pay for security to show he is not breaking the rules.
"With the trees and serenity, being in this kind of environment is a blessing," Djokovic told the New York Times.
"I'm grateful, because I've seen the hotel where the majority of players are staying. I don't want to sound arrogant... but it's tough for most of the players, not being able to open their window and being in a hotel in a small room."
Djokovic contracted COVID-19 during his Adria Tour exhibition tournament in June.
He was heavily criticised for the event but says it has become a "witch hunt".
"We tried to do something with the right intentions," Djokovic said.
"Yes, there were some steps that could have been done differently...but if I had the chance to do the Adria Tour again, I would do it again."