Goran Ivanisevic, Novak Djokovic's coach, is the latest figure from the Adria Tour to contract coronavirus.
The 2001 Wimbledon winner posted on Instagram he tested positive for COVID-19 after two negative tests during the past 10 days.
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"I would like to inform everyone who has been in contact with me that I tested positive and ask them to take extra good care of themselves and their loved ones," Ivanisevic wrote. "I will continue to self-isolate as I have been doing already."
Ivanisevic joins Novak Djokovic, Borna Coric, Grigor Dimitrov and Viktor Troicki testing positive for the virus.
The players all tested positive after playing the Djokovic-led charity exhibition event, which launched in Belgrade and stopped in Zagreb, Croatia, which is where Dimitrov first reported feeling sick.
Ivanisevic, who was in the stands for the Adria Tour, said he felt no symptoms before his positive test and plans to continue self-isolating. Ivanisevic joined Djokovic's coaching team in June, 2019.