Bernard Tomic heavily criticised the Covid-19 testing protocols at the Australian Open qualifying, during an on-court conversation with the chair umpire.
Tomic's claims came during a 57-minute 6-1 6-4 defeat to Russia's Roman Safiullin.
Down 2-1 in the second set, Tomic told Brazilian chair umpire Aline Da Rocha Nocinto during the changeover that he was struggling physically, before going on to criticise the Covid-19 testing protocols.
"For sure, in the next two days I'll test positive, I'm telling you," Tomic told the official. "I'll buy you dinner if I don't test positive in three days. Otherwise, you buy me dinner.
"I can't believe nobody is getting tested. They're allowing players to come onto the court with rapid tests in their room... come on. No official PCR testing."
The 29-year-old was then unavailable to speak to the media after his match and instead took to social media to post a statement.
"Feeling really sick, I'm now back in my hotel room," Tomic said. "Just spoke to the doctors on site and they've asked me to isolate. They couldn't treat me yet to avoid contact."
Djokovic training but uncertainty remains
Meanwhile, Novak Djokovic is back in training ahead of next week's Grand Slam after winning an appeal against a decision to refuse him a visa, but questions remain regarding his whereabouts last month around the time he tested positive for Covid-19 and regarding a travel declaration form.
In his travel declaration form, filed on January 1, Djokovic answered "no" to the question: "Have you travelled, or will you travel, in the 14 days prior to your flight to Australia?".
Djokovic flew to Melbourne from Spain on January 4, but had appeared in photos posted to social media by journalist Jose Morgado from Belgrade on Christmas Day.
The Federal Immigration Minister Alex Hawke still retains the personal power to cancel the athlete's visa, despite his successful court case.
A spokesperson for Minister Hawke on Monday said it was within his "discretion to consider cancelling Mr Djokovic's visa under his personal power of cancellation within section 133C(3) of the Migration Act".
"The Minister is currently considering the matter and the process remains ongoing."
The Australian Open draw takes place on Thursday, with the competition set to start on Monday, January 17.
Djokovic has won this first Grand Slam of the year nine times and has amassed 20 major titles in his career. If he remains in Australia and is successful once again, he would eclipse both Roger Federer and Rafael Nadal in terms of all-time Grand Slam singles titles.