A former Australian Open quarter-finalist has warned that “caged” Novak Djokovic would be a fearsome opponent on court if he makes it out of quarantine.

Like the Serbian superstar, Tennys Sandgren is not jabbed against COVID, but the American has chosen to miss his first Australian Open in a decade because of his vaccination status.

He told Sky News from his home in Nashville, Tennessee: “I haven’t lost a moment of sleep over it, I feel it is a potentially slippery slope that we are going down, and we are being forced to take things we don’t want to take.”

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“I am resolute and sticking with what I believe in, even if it hurts my career,” he continued.

“Maybe this thing calms down in a year – that’s kind of what I am hoping, my plan is to play in the States until the US Open…one slam is better than none.”

Sandgren, 30, who made the quarter-finals in 2018 and 2020, said that Djokovic’s predicament, being held in a quarantine hotel in Melbourne after Australia cancelled his visa, has become “pretty wild”.

“I’d probably just go home,” he said.

“I’m not sure if I would follow through with the lawsuit on Monday… I can see why you would do that if you feel you have been treated unjustly or in an unfair manner….For me I’d just go home.”

During the 2018 tournament, Sandgren was forced to deny he is homophobic or a right-wing sympathiser after scrutiny of his social media profiles and messages.

He issued an apology after it emerged he had followed a number of people with extreme political views.

While Djokovic’s family have said he is struggling to sleep in the cramped quarantine hotel room, Sandgren said if he does somehow get permission to play, he wouldn’t want to face him on court.

“You can see him walking on the court and getting a plethora of boos and jeers and playing just fine,” Sandgren added.

“I don’t want to play him anyway, let alone when he has been locked up in a cage, quote unquote, for a few days – I don’t want to see that!”

He said the Serbian’s determination could still see him win his case and is one of the reasons why he has been so successful through his career: “When he is determined, he won’t let go ever – he will literally dig to the depths of his soul to not be stopped.”