Melbourne,  Russian tennis star and world No. 5 Andrey Rublev has become the latest player to test positive for COVID-19 with three weeks remaining for the start of the opening Grand Slam of the year -- the Australian Open -- from January 17.

On Sunday, another top player, world No. 14 Denis Shapovalov of Canada had tested positive for the virus while in Sydney.

Rublev was scheduled to play in the multi-nation ATP Cup from January 1, where Russia begin their campaign against Austria in Sydney. But that is out of question now as Rublev, the Australian Open quarterfinalist this year, completes his isolation in Barcelona, where he resides.

Three of the world's top players -- Rafael Nadal, Shapovalov and now Rublev -- have tested positive after recently playing in an Abu Dhabi exhibition event. A total of six players have now tested COVID-positive since the conclusion of the event.

On Monday, Rublev posted a message on social media saying, "I want to share some news with you. I am currently in Barcelona and unfortunately tested positive for COVID-19. I have minimal symptom. I am in isolation and following all the protocols under the supervision of doctors. As you know, I am fully vaccinated and was preparing for tournaments -- ATP Cup and Australian Open. Now I have to recover and I will go to Melbourne only when it will be safe for everyone.

"I am very upset and concerned about what is happening. I will return to the court as soon as possible," added Rublev.