Rafael Nadal announced on Monday that he has tested positive for COVID-19. This comes after Nadal arrived back in Spain after competing in the Mubadala World Tennis Championship exhibition event in Abu Dhabi just days ago.

The 20-time Grand Slam champion said he is dealing with some "unpleasant moments" with the virus, but was hoping that he'd be on the mend soon.

"I wanted to announce that on my return home after playing the Abu Dhabi tournament, I have tested positive for COVID in the PCR test that has been performed on me when I arrived in Spain," Nadal posted on Twitter.

Nadal also stated that he had tested negative when he was competing in Abu Dhabi and even returned a negative test on Friday.

"As a result of the situation I have to have total flexibility with my calendar and I will analyse my options depending on my evolution. I will keep you informed of any decisions about my future tournaments."

The tournament in Abu Dhabi was Nadal's first after dealing with a left foot injury. The injury forced the Spanish star to withdraw from the US Open just 10 days before the Grand Slam event. Nadal was also forced to miss the Tokyo Olympics in addition to the US Open.

His status for the Australian Open, which is set to get underway on Jan. 17, is now up in the air.