Novak Djokovic’s coach Goran Ivanisevic is the latest person involved with the world number one’s Adria Tour to test positive for coronavirus.
Former Wimbledon champion Ivanisevic, 48, was the director of the Croatian leg of the event organised by Djokovic.
Serbia’s Djokovic apologised after becoming the fourth player – along with Grigor Dimitrov, Viktor Troicki and Borna Coric – to test positive.
Ivanisevic urged people he has been in contact with to “take extra care”.
The Croat said he is “feeling good” and does not have any symptoms.
He added: “I will continue to self-isolate as I have been doing already. I wish everyone who got infected a speedy recovery.”
Djokovic, a 17-time Grand Slam champion, was criticised for his role in the event, which was held in front of fans and without social distancing rules being observed.
The first leg in Serbia attracted 4,000 fans, and players were later pictured dancing close together in a Belgrade nightclub.
In Croatia, players including Djokovic and Ivanisevic were pictured taking part in a basketball match.
Djokovic, 33, said they had “met all health protocols” in the two countries, which have relatively low levels of recorded Covid-19 cases.
But, after announcing his positive test on Tuesday, he added: “We were wrong and it was too soon.”