Sunday's Adria Tour final has been cancelled after Grigor Dimitrov revealed he has tested positive for coronavirus.
Dimitrov competed in the Serbian and Croatian legs of the exhibition tournament along with Novak Djokovic, Alexander Zverev and Dominic Thiem.
The world number 19 lost in straight sets to Borna Coric in the Croatian city of Zadar on Saturday and returned home to Monaco after complaining of feeling unwell.
He has now confirmed he has contracted COVID-19 and the tournament's final, which would have featured Djokovic and Andrey Rublev, has been called off as a result.
Dimitrov took to social media on Sunday to issue an apology for potentially putting others at risk and forcing the competition to finish prematurely.
"I want to reach out and let my fans and friends know that I tested positive back in Monaco for COVID-19," he posted on Instagram.
"I want to make sure anyone who has been in contact with me during these past days gets tested and takes the necessary precautions.
"I am so sorry for any harm I might have caused. I am back home now and recovering. Thanks for your support and please stay safe and healthy."