Novak Djokovic tested positive for the coronavirus and has entered a 14-day self-quarantine.
The top-ranked Djokovic was the fourth player to test positive at his organized tournament in Serbia, which was canceled before the finals. Djokovic said he has not yet experienced symptoms common with the coronavirus.
ATP player council member Bruno Soares said the tournament, which did not include safety protocol or health regulations, was a "horror show" not long after images surfaced of Djokovic and other players from the tournament field dancing shirtless in a nightclub.
"Enormous irresponsibility and huge immaturity," Soares told the NY Times. "They were totally careless and it's difficult for me to find the words."
Djokovic issued a statement on Tuesday detailing the purpose of the event and his positive COVID-19 test:
"The moment we arrived in Belgrade we went to be tested. My result is positive, just as Jelena's, while the results of our children are negative. Everything we did in the past month, we did with a pure heart and sincere intentions. Our tournament meant to unite and share a message of solidarity and compassion throughout the region.
"The Tour has been designed to help both established and up and coming tennis players from South-Eastern Europe to gain access to some competitive tennis while the various tours are on hold due to the COVID-19 situation.
"It was all born with a philanthropic idea, to direct all raised funds towards people in need and it warmed my heart to see how everybody strongly responded to this. We organized the tournament at the moment when the virus has weakened, believing that the conditions for hosting the Tour had been met.
"Unfortunately, this virus is still present, and it is a new reality that we are still learning to cope and live with. I am hoping things will ease with time so we can all resume lives the way they were. I am extremely sorry for each individual case of infection. I hope that it will not complicate anyone's health situation and that everyone will be fine.
"I will remain in self-isolation for the next 14 days, and repeat the test in five days."
Tennis players Viktor Troicki, Grigor Dimitrov and Borna Coric have also tested positive for the coronavirus.