Alexander Zverev has revealed he was suffering with a fever during his French Open defeat to Jannik Sinner.
Highly rated Italian Sinner became the first player since Rafael Nadal in 2005 to reach the quarter-finals at Roland Garros on his tournament debut, beating Zverev 6-3 6-3 4-6 6-3 to progress.
But Zverev's post-match comments have taken the spotlight from Sinner, as the German claimed he was playing despite showing symptoms of a respiratory illness.
Due to the COVID-19 pandemic, players are expected to undergo regular coronavirus tests, socially distance where possible and wear a mask when not on court.
Competition rules state a player will be removed from the draw if they come into contact with a player or entourage member who has tested positive for the virus.
Zverev said any tests he has done have been negative, likewise those in his circle, though he accepts he should not have played on Sunday.
He said: "I am completely sick after the match with [Marco] Cecchinato in the night. Yeah, what can I say? I'm completely sick.
"I can't really breathe, as you can hear by my voice. I had fever, you know, as well. Yeah, I'm not in the best physical state, I would say.
"I think that had a little bit of an effect on the match today."
Zverev added: "To be honest, I warmed up today. I shouldn't have played. But I was hoping maybe for a three-set win or something like that, but I knew from the beginning that it wasn't going to be easy."
But when asked in the English section of the news conference about when he last had a coronavirus test, Zverev took issue with the journalist asking the question.
"I'm not answering your questions. There is no chance I'm answering your questions from what you have been writing about me over the past months. Absolutely no chance," he said.