Kei Nishikori, the 2014 US Open runner-up, said he tested negative for Covid-19 after having two positive tests but still decided to withdraw from the Grand Slam tournament that begins next week.
Nishikori wrote Wednesday on his mobile app that he is ready to slowly return to practice but not prepared to compete in best-of-five-set matches.
"After such a long break I feel that returning in a best of 5 long-match setting is not smart until I am fully ready to do so," Nishikori's post said. "It's disappointing as I love the US Open and have great memories there. I will start on the clay. Thank you."
The US Open, on the hard courts at Flushing Meadows, ends on Sept. 13. Then the tennis tour shifts to red clay in Europe, with tuneup tournaments planned ahead of the scheduled start of the French Open on Sept. 27.
Nishikori said last Friday he tested positive for Covid-19 a second time and had very minimal symptoms.
The 30-year-old from Japan has been ranked as high as No. 4 and is currently No. 31, which would have put him in line to be seeded for the US Open.
Nishikori lost in the 2014 final at Flushing Meadows to Marin Cilic and was also a semifinalist in New York in 2016 and 2018.