Japan's Kei Nishikori said Friday he has tested positive again for the novel coronavirus after revealing his initial infection less than a week ago, making it very unlikely he will play at the U.S. Open starting Aug. 31.
"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 his official app.
Following the initial positive test, the 30-year-old pulled out of the Western and Southern Open, a U.S. Open warm-up event moved to New York from its normal venue in Cincinnati.
"(My) next test will be early next week at which time we will update you with more information. Thanks for all the messages and have a good weekend," added Nishikori.
The Japanese had his career-best Grand Slam result at the U.S. Open in 2014 when he finished runner-up.
He reached the semifinals in his past two appearances at the year's final Grand Slam, in 2016 and 2018.
The ATP Tour resumed this month after a five-month hiatus due to the pandemic. The U.S. Open will be held without spectators for infection prevention purposes and players who tested positive to the virus will be ineligible.
A number of players have already withdrawn from the tournament, including defending men's singles champion Rafael Nadal and women's singles world No. 1 Ashleigh Barty.