Rafael Nadal has tested positive for Covid-19 in a development that could throw his Australian Open participation further into doubt. The 20-time grand slam champion returned to action last week after more than four months out with a foot problem, suffering defeats to Andy Murray and Denis Shapovalov on Friday and Saturday at an exhibition event in Abu Dhabi. Posting on social media on Monday morning, Nadal wrote: “Hello everyone. I wanted to announce to you that on my return home after contesting the Abu Dhabi tournament, I have tested positive for Covid in the PCR test that was performed on me upon arriving in Spain. Both in Kuwait and Abu Dhabi we passed checks every two days and all came back negative, the last being on Friday and having results on Saturday. “I am having some unpleasant moments but I hope that I will improve little by little. I am now confined at home and I have reported the result to people who have been in contact with me. As a consequence 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 posted on any decisions regarding my future tournaments! Thank you all in advance for the support and understanding.” Nadal’s foot problems flared up after his gruelling loss to Novak Djokovic in the French Open semi-finals in June. He pulled out of Wimbledon and the Olympics and then called time on his season in August after playing an ATP tournament in Washington. Speaking after his defeat by Shapovalov at the weekend, Nadal admitted he could not guarantee his participation at the Australian Open. Most players are due to head to Australia shortly after Christmas for the start of the new season. There are not currently expected to be any quarantine requirements but, with Covid-rates soaring in a number of countries, the virus could well have a significant impact on the tournament.