World number three Dominic Thiem is "extremely sorry" for the way players conducted themselves at Novak Djokovic's Adria Tour exhibition event after which four players tested positive for the novel coronavirus, the Austrian said on Thursday.
Djokovic, Grigor Dimitrov, Borna Coric and Viktor Troicki tested positive after playing in the charity tournament in Serbia and Croatia, which drew big crowds and saw players pose for pictures together.
Images and videos of the players hugging at the net, playing basketball together and partying at the event have also been posted on social media.
"We played without an audience for weeks, so we have been more than happy about the fans at the event," Thiem said in an Instagram post. "We trusted the Serbian government's corona rules, but we have been too optimistic.
"Our behaviour was a mistake, we acted too euphorically. I am extremely sorry."
Though the players were not breaking government protocols during the tournament, it highlighted the risks of athletes from different countries mingling without adhering to what have become social distancing norms.
Thiem, also a two-times finalist at Roland Garros, did not play in Zadar as he had signed up to join the Ultimate Tennis Showdown, which is being held on weekends at Patrick Mouratoglou's academy in France.
"I've now got tested five times within the last ten days and the result was always negative. I wish everyone who is infected all the best and quick recovery," Thiem added.