NEW YORK -- Kei Nishikori, the 2014 US Open runner-up, said Friday he tested positive for COVID-19 a second time.
Nishikori wrote on his mobile app that he will take another test next week, "at which time we will update you with more information."
"I have very minimal symptoms and am staying in full isolation," Nishikori wrote Friday.
He cannot play in the US Open, which begins Aug. 31, if he has COVID-19.
Nishikori originally tested positive for the illness caused by the coronavirus on Sunday and announced that day he was pulling out of the Western & Southern Open, the hard-court tournament that starts Saturday and precedes the US Open in New York.
The 30-year-old from Japan has been ranked as high as No. 4 and is currently No. 31, which puts 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.