Both Borna Coric and Grigor Dimitrov have tested positive for COVID-19 after attending an event hosted by Novak Djokovic.
The pair tested positive after playing in Djokovic's charity event, and his opponent in the Croatian leg of the Adria Tour, Borna Coric, confirmed he too tested positive.
"I want to make sure anyone who has been in contact with me during the last few days gets tested!" the Croatian tweeted.
"I am really sorry for any harm I might have caused! I'm feeling well and don't have any symptoms."
Dimitrov and Coric played each other over the weekend, embracing at the net before the match but only bumping fists afterwards.
Djokovic's Serbian Davis Cup teammate, Viktor Troicki, also tested positive after playing in the tournament.
Tennis.com reported that Dimitrov's coach, Christian Groh, and Djokovic's fitness coach, Marco Panichi, also tested positive.
Djokovic organised the Adria Tour to be played in four legs in Serbia, Croatia, Montenegro and Bosnia and Herzegovina.
Djokovic has been heavily criticised for hosting the tournament during the pandemic, but tried to reassure people last week that the organisers were adhering to government guidelines around safety.
"Of course lives have been lost and that's horrible to see, in the region and worldwide, but life goes on, and we as athletes are looking forward to competing," he said.
However Aussie tennis star Nick Kyrgios has taken his chance to swipe at Djokovic slamming the choice to run the event.
"Boneheaded decision to go ahead with the 'exhibition'," he wrote.
