Borna Coric is the latest tennis player to test positive for coronavirus after playing on the Adria Tour.
World number 19 Grigor Dimitov announced on Sunday that he had returned a positive COVID-19 test.
He had faced Coric on Saturday, with the Croatian now also warning those he has been in contact with that he has been asymptomatic.
"Hi everyone, I wanted to inform you all that I tested positive for Covid-19," he wrote on Instagram.
"I want to make sure anyone who has been in contact with me during the last few days gets tested! I am really sorry for any harm I might have caused!
"I'm feeling well and don't have any simptoms(sic). Please stay safe and healthy! Lots of love to all!"
The Adria Tour events were organised by Novak Djokovic to help players get back up to speed after weeks of inactivity due to the pandemic.
The most recent tournament in Zadar – where world number one Djokovic was set to play in Sunday's final – was cancelled following Dimitrov's test.
But that was not enough for outspoken Australian Nick Kyrgios, with the world number 40 unhappy the event took place at all.
"Boneheaded decision to go ahead with the 'exhibition' speedy recovery fellas, but that's what happens when you disregard all protocols. This IS NOT A JOKE," he posted on Twitter.