Alexander Zverev admitted he "should not have played" after he revealed he was suffering with a "fever" in the lead up to his defeat to Italian teenager Jannik Sinner in the French Open fourth round.
The German sixth seed called for the doctor early into his 6-3 6-3 4-6 6-3 loss to the world No 75, and revealed after the match that he had had a temperature of 38 Celsius during the night after his previous match against Marco Cecchinato on Friday.
Players at Roland Garros have regular Covid-19 tests, but tournament organisers revealed on Sunday evening that Zverev's last test was on September 29 and that he had not sought advice before playing.
A statement from the French Tennis Federation said: "Zverev is up to date on his tests, which have all been negative. His last test was on September 29, with results received on September 30.
"Today he received a reminder for his next test, to be carried out within five days of the previous results. He did not consult the tournament doctors before his match."
Zverev, who kept his face mask on during his post-match press conference, said: "I'm completely sick. I can't really breathe, as you can hear by my voice. I had a fever as well. I shouldn't have played."
Sinner, the reigning Next Gen ATP Finals champion, produced an excellent performance, belying his Grand Slam inexperience, to convert five of his six break-point opportunities against Zverev and is the youngest Grand Slam men's quarter-finalist since Novak Djokovic 14 years ago.
Zverev threatened a comeback by winning the third set, but Sinner showed his resolve to come out on top in a series of close games in the fourth set before serving out the biggest win of his career.
"Today was very tough, knowing that it was going to be a long match," said Sinner. "At the end, I am very happy about my performance."
The world No 75 will next face 12-time champion Rafael Nadal in the ultimate clay-court test, becoming the first player since the Spaniard to reach the quarter-finals in Paris on his main draw debut.
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Nadal reached the last eight at Roland Garros for a record 14th time with a 6-1 6-1 6-2 win against American qualifier Sebastian Korda.
"Sebastian will have a really bright future, such a great player and only 20 years old," said Nadal.
"It is a real honour [he idolises me]. All of our generation try hard to be passionate, play every single day at our best, and if that is an inspiration for the younger generation, that is good."
Korda, another French Open debutant, had two break points in a nine-minute opening game but could not capitalise as Nadal quickly asserted his command.
The American did break early in the third set, but Nadal responded by winning the next five games in succession to seal a one-sided victory.
The second seed said: "I'm in the quarter-finals without losing a set and having very positive scores. So I can't complain at all.
"I am quite happy about the way that I am playing and the practices I am feeling every time a little bit better and better. Today the conditions out there have been so difficult to play a fantastic match because the wind was very high. But in general terms I am very happy."
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