Novak Djokovic is a nine-time Australian Open champion - but serious doubts persist as to whether he'll be playing for a tenth title in January.
Djokovic, 34, is just one Grand Slam win away from a record breaking 21st major crown, but his participation in Melbourne could be in jeopardy due to his stance on the Covid-19 vaccine.
The Serbian star has long been vocal about his belief the the vaccine shouldn't be mandatory for players to take part in tour events, and has refused to reveal if he's been jabbed himself.
If so, it is likely he will be refused the chance to play in the Open, with Victoria's State Premier Daniel Andrews adamant players will not take part unless they have taken the vaccine.

The Canberra Government is said to be open to allowing unvaccinated individuals into the state, providing they serve a quarantine period, but Andrews has remained unrelenting with his stance.
Reportedly, around 25% of ATP and WTA players remain unvaccinated, and now the world no 1 has said he, and other, will delay any decision until they hear from Tennis Australia.
"I'm going to decide on whether I go or not after I see the official statement from Tennis Australia," he said.
"I'll see what I personally do with that and also the bigger group of players. Because the situation is obviously different in Australia than in most parts of the world."
Indeed, Djokovic may not be the only male star missing.

Russian player and world no 2 Daniil Medvedev, who prevented the Serbian from claiming a coveted 21st Slam when he beat him in the US Open final at Flushing Meadows in September, was non-committal when asked about the same issue..
"I'm willing to play Australia, but I won't say if you'll see me there, we're going to see in January," he said.
"If you're playing Australia, it's obvious you are vaccinated. I just keep my medical records to myself."
World no 3 Stefanos Tsitipas has also previously said he disagreed with the notion that players should be vaccinated to take part in tournaments.
However, Andy Murray is one star to hold an opposing view, saying last month he would support any restrictions imposed on unvaccinated players.