A "sick" Alexander Zverev said he "should not have played" after he lost in the French Open fourth round to Italian teenager Jannik Sinner.
The German sixth seed called for the doctor during his 6-3 6-3 4-6 6-3 defeat and later said he had a "fever".
The 23-year-old was up to date with his tournament-organised Covid-19 tests, with his last one on 29 September.
But a French Tennis Federation (FFT) statement said: "He did not consult the tournament doctors before his match."
Zverev told reporters he had a temperature of 38 Celsius during the night after his previous match against Marco Cecchinato on Friday.