The Federal Circuit Court of Australia on Monday overturned the government's decision to refuse Djokovic a visa upon his arrival in Melbourne on Wednesday, after which the world No 1 spent four nights in an immigration detention hotel.

Following his release on Monday, Djokovic, a record nine-time winner of the Australian Open, announced his intention to defend his title at the first Grand Slam of the year, which gets under way on Monday, January 17. The draw is set to take place on Thursday.

Asked about Djokovic's prospects of winning the tournament, Castle told Sky Sports News: "I wouldn't be surprised.

"He's such a stubborn and hard-working guy on court, if he gets this exemption and if the Australian government don't supersede the court, I would say that he's going to tee it up and play.

"If he can get through two, three, four rounds, and play his way into the tournament - we know how good he is - I wouldn't be at all surprised to see him into the second week of this grand slam once again, because he is so stubborn and so good.

• Djokovic back in training | 'I want to stay and compete'
• Djokovic debacle: Key questions after successful appeal

"When it's time, and the bell rings, he'll be ready to compete. Sometimes Novak can be even better when everyone is against him than when everyone is for him."

Following the verdict on Monday, Djokovic tweeted to say he would "remain focused" on competing in front of Australia's "amazing fans", but Castle has warned that the 34-year-old can expect a hostile atmosphere from spectators when the tournament begins.

"When it comes to the crowd reaction, I suspect they'll boo him roundly when he comes out on court and I think the whole thing will turn into a massive pantomime," Castle said.

"But let's make no mistake, Covid is not to be fooled with, Omicron is not to be fooled with, but the Australians, many of them are absolutely terrified. They're undergoing a huge wave over there and this is a man who, waving his medical exemption around, said 'I'm on my way down'.

"It was unsubtle, it was tone deaf and it was a PR disaster for him, kind of igniting this whole debate and, who knows, might have influenced the action of the government as well.

"He can stand on his own two feet. But he can expect a tough reaction."

Questions remain over December 16 whereabouts

There is still confusion surrounding Djokovic's movements around December 16, the date he tested positive for Covid.

Djokovic attended an event on December 16 at the Belgrade headquarters of the Serbian national post office, which was honouring him and his career with the release of a series of stamps.

Djokovic posted pictures from the event - in which he is seen maskless - on his Twitter account on December 17.

It is unclear if Djokovic knew he had Covid when he attended the event.

When asked about his whereabouts around December 16, his brother Djordje Djokovic said in Monday's press conference: "The process was public and all the documents are public and legal."

When asked again by another reporter, he said: "OK, so this press conference is adjourned at the moment, thank you for your attention," before abruptly ending the conference, which prompted applause.