Japan's Kei Nishikori has tested positive for coronavirus and will not play in the Cincinnati Masters, with the US Open two weeks away.
The 2014 US Open runner-up, 30, says he is "feeling well" but will now isolate and get tested again on Friday.
Defending champions Rafael Nadal and Bianca Andreescu have already said they will not compete at Flushing Meadows.
"This morning while still in Florida, I got tested for Covid-19 and tested positive," said the world number 31.
"I will have to pull out of the Cincinnati tournament at this time.