America's Denis Kudla was told he had tested positive for the coronavirus mid-match at the Australian Open qualifying tournament - and then sealed victory before going into quarantine.
The fourth seed learned of the positive test when 5-3 up in the second set against Moroccan Elliot Benchetrit, but was allowed to complete the ninth game.
Kudla, the world No 114, clinched the match 6-4, 6-3, but was then pulled out of the tournament and placed in hotel quarantine.
"My opponent tested positive during the match, at 5-3," Benchetrit said on Instagram.
"If I'd won the game at 5-3 to make it 5-4, I would have qualified for the second round."
Kudla's scheduled opponent, Australian wildcard Dane Sweeny, was given a walkover into the final round.
Kudla was not the only player to test positive at the men's qualifying tournament, which is being held in Doha because of quarantine restrictions in Melbourne.
Argentinian player Francisco Cerundolo was yet to play his first-round match against Mario Vilella Martinez of Spain when he learned of his positive test.
"Two players have returned a positive Covid-19 test at AO men's qualifying in Doha, Qatar," Tennis Australia tweeted.
"Both players have been withdrawn from the tournament and transferred to a quarantine hotel."
Preparations for the Australian Open have been badly disrupted by the coronavirus outbreak, with the tournament's start date pushed back three weeks to 8 February.
Strange scenes in Doha.— TENNIS (@Tennis) January 12, 2021
Denis Kudla led Elliot Benchetrit, 6-4, 5-3, when both learned the American tested positive for COVID-19.
They were permitted to finish the game in progress before Kudla was withdrawn. Had Benchetrit won it, he'd be in round two.https://t.co/r1Y5YUubbs