Fans of Novak Djokovic are outside of his hotel.
Australian player Nick Kyrgios said that his country's handling of the visa dispute was really bad and urged officials to do better.
The world number one is facing deportation after being denied entry to the country.
"This is one of our great champions, but at the end of the day, he is a human," said Kyrgios.
An urgent court challenge was launched by the Serbian tennis player on Monday, a week before the Australian Open begins.
Foreign visitors to Australia must be double vaccined. They have to complete 14 days in quachicle.
The medical exemption granted to the 20-time Grand Slam champion, who has previously said he is opposed to vaccination, angered many Australians.
Tennis Australia, the body that runs the Australian Open, and Victoria state, tournament organizers said that the exemption was given by two independent medical panels.
Scott Morrison, the country's prime minister, said that if he failed to provide proper medical proof for his exemption, he would be sent home.
The decision on whether or not to allow him to stay in the country is still pending after he was questioned for hours about his exemption evidence.
In the past, he has been a critic of the Serbian.
He said that the exhibition event in the Balkans wasbone-headed because the Serb and several others had tested positive for coronaviruses.
The Australian Open was asked to ease the restrictions on players last year, and they were called a tool by the player.
The Australian has spoken out about the treatment of the Serb as he waits for the outcome of the appeal.
He said he got the vaccine because of others and for his mother's health.
How we are handling Novak's situation is really bad. Do better.
Nick and Novak have had a difficult relationship.
John Isner said there was no justification for the treatment received by the Serbian.
"What Novak is going through right now is not right," said Isner, who also wrote #IstandWithNovak in the post.
He followed the rules, was allowed to enter Australia, and now he's being held against his will. This is a shame.
Canadian player Vasek Pospisil, who set up the Professional Tennis Players Association (PTPA) with the Serb, urged him to stay strong.
The organization said it had been in close contact with the man.
He has requested that we allow him to personally share the facts of his detainment in his own words, and in his own time," the body said.
Marin Cilic, who won the US Open in 2004, said the episode was not good for the sport and hoped it would be resolved quickly.
The Croat said it was not a good picture for tennis.
Jelena thanked people for using their voice to send love to the player.
We wish we were all together today, but I am happy that we are healthy. She wrote that they would grow from the experience.
The Australian Open men's singles title has been won nine times by the Serbian. The Grand Slam tournament will be held in January.
