Kyrgios on Friday defended Djokovic, who is locked up in hotel quarantine in Melbourne and facing deportation after arriving in Australia without a proper medical exemption from COVID19 vaccination.

The Serb's lawyers are fighting the decision to cancel his visa that could scupper his shot at a record-breaking 21st grand slam title.

As the furore escalated, a second player, Czech doubles specialist Renata Voracova, was placed in the same hotel by Australian Border Force with her visa reportedly cancelled despite having already played an event in Melbourne this week.

She, like Djokovic, was said to have received a vaccine exemption from Tennis Australia on the basis she had been infected with COVID-19 in the last six months.

The Czech Foreign Ministry in Prague said it had sought an explanation but also that Voracova had decided to leave the country.

Kyrgios is pro vaccination but called Djokovic's situation "really bad".

"Look I definitely believe in taking action, I got vaccinated because of others and for my mum's health, but how we are handling Novak's situation is bad, really bad," the 26-year-old tweeted.

"Like these memes, headlines, this is one of our great champions but at the end of the day, he is human. Do better."

Kyrgios blasted the Serbian superstar in 2020 for his ill-fated Adria tour, calling it a "bone-headed decision" and then described him as a "tool" after the nine-time Open champion's comments about quarantine last year.

But Kyrgios said late last year he felt it was "morally wrong" to force people like Djokovic to get vaccinated against COVID-19.

The Professional Tennis Players Association, an organisation founded by Djokovic and Canadian player Vasek Pospisil, issued a statement on Friday following contact with the world No.1.

It read: "The PTPA has been in close contact with Mr Djokovic, his family and legal counsel, government officials and Australian Open leadership. Mr Djokovic has verified his well-being to us.

"He has also requested that we allow him to personally share the facts of his detainment in his own words, and in his own time."

Kyrgios is not the first player to throw his support behind Djokovic.

Anti-vaxxing two-time Open champion Tennys Sandgren on Thursday said Australia didn't deserve to host a grand slam after following its clumsy handling of the Djokovic saga.

Meanwhile, Djokovic's wife Jelena on Friday used social media to express her gratitude to her husband's legion of fans.

In Instagram and Twitter posts marking Christmas in Serbia, Jelena Djokovic wrote: "Thank you dear people, all around the world for using your voice to send love to my husband.

"I am taking a deep breath to calm down and find gratitude (and understanding) in this moment for all that is happening.

"The only law that we should all respect across every single border is love and respect for another human being."

A small crowd of protesters gathered on Friday outside of Djokovic's Melbourne hotel, which also houses about 30 refugees.

The dean of Melbourne's Holy Trinity Serbian Orthodox Church, Father Milorad Locard, reportedly sought to visit Djokovic on Friday to mark the Orthodox Christmas with him.

"That he has to spend Christmas in detention centre, it is unthinkable," he told the ABC.

At a protest and press conference in Belgrade Djokovic's father Srdjan claimed the 20-time grand slam winner had been "crucified" by Australian authorities.

"He met all the required conditions for the entry and participation at the tournament that he would have certainly won, since it's Novak, the best tennis player and sportsman in the world," Djokovic senior said.

"Jesus was crucified and endured many things, but is still alive among us. Novak is also crucified... He will endure."

Australian Associated Press