Jan. 15 (UPI) -- American tennis star Madison Keys has tested positive for COVID-19 and will miss the 2021 Australian Open. Rafael Nadal's coach also will miss the Grand Slam due COVID-19-related issues.
"I unfortunately tested positive for COVID-19 before I was supposed to fly to Australia," Keys wrote Thursday on social media.
"I'm very disappointed to not be able to play in the coming weeks after training hard in the off-season and knowing Tennis Australia and the tours did so much to make these events happen."
Keys -- the No. 16 player in the WTA world rankings -- said she is isolating at home and will continue to follow health precautions.
"I look forward to being back on tour next month," Keys wrote.
Keys, 25, reached the semifinals at the 2015 Australian Open and the quarterfinals at the 2018 Australian Open, but lost in the third round of last year's Grand Slam in Melbourne. She has yet to win a Grand Slam.
Nadal's coach, Carlos Moya, said he will not join the world's No. 2 player in Melbourne due to health restrictions tied to the pandemic.
"After speaking with Rafa, we have decided that I won't travel to Australia with the team," Moya wrote Wednesday on Twitter.
"I will follow the tournament from home and will stay with my family, parents and kids due to the delicate situation that Spain is [having] with the virus. Best of luck to the team!"
Nadal has 20 career Grand Slams, but just one Australian Open crown (2009).
World No. 3 Dominic Thiem, who reached the finals of the men's singles circuit last year in Melbourne, could be without coach Nicolas Massu at this year's tournament. Massu tested positive for COVID-19 and did not travel to Australia this week as scheduled.
"Before we took off, we received the surprising message from Nicolas Massu that he had a positive test," Thiem's father, Wolfgang, told Austria's Kurier.
Men's tennis star Andy Murray also is in doubt for the tournament after he tested positive for COVID-19. Murray had planned to fly to Melbourne this week, but now will need to be granted permission for a later arrival. Other Australian Open competitors and officials were required to arrive by this weekend.
The 2021 Australian Open starts on Feb. 8.
Players at this year's Australian Open must pass a series of COVID-19 tests during a 14-day quarantine in Melbourne before they compete in the Grand Slam. They are allowed to practice during the quarantine.