All players must be vaccinated or have an expert-approved exemption. While Djokovic has not confirmed that he is unvaccinated, he has said he is "opposed to vaccination".
He will be aiming to win a fourth consecutive Australian Open men's singles title. He already holds the all-time record with nine and would love to add a 10th this month.
Medvedev bids to go one better
In last year's final Djokovic defeated Daniil Medvedev and the market makes him Djokovic's closest rival at 3.55/2.
The Russian arrives on a high after winning his first Grand Slam at the 2021 US Open.
Medvedev beat Djokovic in straight sets in the final to avenge his defeat at the start of the year in Melbourne.
Alexander Zverev comes next in the betting at 5.24/1. The German has been knocking at the door of Grand Slam glory for a few years, reaching the semi-final in Melbourne and a final in New York.
Last August, Zverez won the gold medal in the men's singles at the Tokyo Olympics.
Djokovic, Medvedev and Zverev are very much the trio of leading men in Melbourne.
After that comes Rafael Nadal 15.014/1 who won this title in 2009. The 35-year-old's 2021 season was shortened by injury and fans will be hoping he returns gunning for glory.
Nadal is currently bidding to prove his fitness at the ATP Melbourne.
Stefanos Tsitsipas is as long as 38.037/1 in the market. He reached the semi-finals 12 months ago, following a memorable five-set win over Nadal from 2-0 down in the quarters, and went on to reach the final of the French Open.
The Greek's season nosedived after that, though, with first and third round exits at Wimbledon and the US Open respectively, which may in part explain his long odds here.