Rafa Nadal said on Monday (Dec 20) he had tested positive for Covid-19 after returning from his comeback appearance at the Mubadala World Tennis Championship exhibition event in Abu Dhabi last week.
The 20-times Grand Slam champion and former world number one said he was having some "unpleasant moments" but was hoping to feel better soon and would keep people informed about his plans over future tournaments.
The positive test casts further doubt on whether the 35-year-old participates in next month's Australian Open - a tournament he has won once and finished runner-up four times - having already said he could not guarantee he would play.
"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 wrote on Twitter.
Nadal said he had tested negative at all times when he was in Kuwait and Abu Dhabi, and had last tested negative on Friday last week.
During his stay in Abu Dhabi, Nadal met former Spanish king Juan Carlos, who tested negative for Covid, Spain's Royal Household said on Monday.
The monarch, who lives in the United Arab Emirates, is feeling good, the palace added.
Nadal's comeback from injury at the exhibition event - his first tournament appearance since the Citi Open in Washington in August - ended in two defeats by Andy Murray and Denis Shapovalov.
"I am having some unpleasant moments but I hope that I will improve little by little. I am now home bound and have reported the result to those who have been in contact with me," he wrote.
"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."