Alexander Zverev claims that COVID-19 could be rife among the Australian Open field.
The men's third seed told reporters on Wednesday that players weren't being tested, despite the furore around Novak Djokovic that saw the Serb deported at the weekend.
Zverev was speaking after he progressed to the 3rd round with a straight sets victory over home favourite, John Millman.
29th seed Ugo Humbert revealed on Wednesday that he tested positive for coronavirus after his 1st round loss to compatriot Richard Gasquet, meaning he must isolate for a week in Melbourne.
But Zverev says the virus could be even more prevalent in the field.
"We are allowed to go outside to eat, allowed to do whatever we want, so I think it's natural that more people get Covid," said the German.
"I think quite a few players had it when they arrived. Quite a few players I think have it now.
"We're not getting tested, so I think if we would get tested there would be probably more positives than there are now, in a way."
Tennis Australia are yet to comment on Zverev's claims, but he is not alone.
Before testing positive himself, Bernard Tomic was suffering with Covid symptoms during the qualifiers, telling a chair umpire, "I’m sure in the next two days I’ll test positive, I’m telling you.
"I’ll buy you dinner if I don’t test positive in three days. Otherwise, you buy me dinner.
“I cannot believe nobody’s getting tested. They’re allowing players to come on the court with rapid tests in their room. Come on."
Tomic tested positive two days after his outburst.
Zverev told his post-match press conference, "I'm here to play the tournament and I understand that there is a lot of cases in Melbourne, there is a lot of cases in Australia all around. So I don't do much outside, I haven't been to any restaurants yet, I haven't been out.
"I haven't been anywhere but the hotel room and the courts, so I'm kind of doing a bubble for myself, simply because I don't want to take any risks and I want to give myself the best chance possible to do well here."