Coric confirmed on Monday that he had tested positive for Covid-19, a day after Bulgarian ace Grigor Dimitrov revealed he had contracted the disease.

Both players were part of Djokovic's contentious new Adria Tour, which began in Belgrade before moving on to Zadar in Croatia.

The final, which was due to be contested between Djokovic and Russian youngster Andrey Rublev, was scrapped on Sunday after news of Dimitrov's positive test, although not before fans had packed the stands for matches and top 10 stars including Djokovic, Dominic Thiem and Alexander Zverev had mingled freely at social events. 

Coric, who had been beaten by Djokovic in their match on Saturday, announced the news of his positive test on Twitter, writing: "I want to make sure everyone who has been in contact with me in the last few days gets tested.

"I'm really sorry for any harm I might have caused!" 

According to reports in Serbia, Djokovic's fitness trainer Marco Panichi has also tested positive for the illness, although 19 others - including the player's coach, Goran Ivanisevic, and brother Djordje Djokovic - returned negative results.

Djokovic himself is said to have declined a test before leaving Croatia to return to Serbia, instead seeking medical advice on his return home as he "feels well" and is not displaying any symptoms.  

Following the news of Dimitrov's positive test and the cancelation of the event, Adria Tour organizer claimed they had "at all times strictly followed the epidemiological measures in place with the countries where the Adria Tour was organized."

However, that has not allayed concerns over why the tour went ahead in the first place, being played in front of packed stands and also seeing players come in close contact including a nightclub party following the first leg in Belgrade.

Australian world number 40 Nick Kyrgios called the decision to proceed with the tour "boneheaded," while wishing those infected a speedy recovery.