Novak Djokovic is "playing by his own rules" and has made vaccinated tennis players "look like fools", world number four Stefanos Tsitsipas has said.

"For sure, he's been playing by his own rules and has been doing what not many players had the guts to do," Greece's Tsitsipas told India's WION news channel.

"Especially after the ATP announced certain criteria for players to enter the country."

Djokovic, who is unvaccinated, had his visa revoked when he arrived in Australia last week, following questions over the vaccine exemption that would have permitted him to enter.

However, on Monday a judge overturned the decision and ordered his release from an immigration detention hotel after finding that border officials had not followed proper procedure.

In an Instagram post on Wednesday, Djokovic admitted to meeting a L'Equipe journalist on 18 December despite knowing he had tested positive for Covid, as well as there being mistakes on his immigration forms.

Australian Prime Minister Scott Morrison held a news conference to update the country about the coronavirus pandemic on Thursday, although he declined to say when a decision about Djokovic might be made.

Tsitsipas, who lost to Djokovic in last year's French Open final, added: "No-one really thought they could come to Australia unvaccinated and not having to follow the protocols... it takes a lot of daring to do and putting the Grand Slam at risk, which I don't think many players would do.

"I chose to go and be 100% ready for whatever was to come and not have to think about anything else."

The ATP, which governs men's tennis, has said 97 of the top 100 male players are vaccinated.

American world number 93 Tennys Sandgren told reporters earlier this month that he had pulled out of the Australian Open because of the vaccine mandate and he opted not to apply for a medical exemption.

Asked if Djokovic should defend his title at Melbourne Park next week, Tsitsipas said: "There are two ways to look at it. One way is that almost every single player is vaccinated and did what they had to do in order to come and perform and play in Australia.

"On the other sense, it seems not everyone is playing by the rules...a very small [minority] chose to follow their own way, which kind of makes the majority look like fools."

The Australian Open begins on 17 January. Djokovic, who is hunting a record 21st Grand Slam men's singles title, has been drawn to play fellow Serb Miomir Kecmanovic in the first round, with Tsitsipas up against Sweden's Mikael Ymer.