His participation is in grave doubt but if Novak Djokovic plays at the Australian Open he will be chasing a record 21st Grand Slam.
AFP Sport highlights five men to watch when the first Grand Slam of the year begins on Monday:
- Novak Djokovic -
The saga surrounding the vaccine-sceptic Serb's touchdown in Australia would surely make a 21st Grand Slam win Djokovic's greatest achievement.
While the debate over whether he should even be allowed to play will rage on -- and ensure he receives a hostile reception from parts of the Rod Laver Arena crowd -- the fact remains that the polarising Serb stands on the cusp of tennis history.
Djokovic has won a record nine championships in Melbourne and is unbeaten on the famous blue courts since his shock last-16 defeat to South Korea's Hyeon Chung in 2018.
His 20 Grand Slam singles titles are matched by Rafael Nadal and Roger Federer, though the ageing Swiss maestro is absent for the second consecutive year because of injury.
- Rafael Nadal -
It remains to be seen if the Djokovic saga plays into the 35-year-old Spaniard's hands as he also strives to be the first man to achieve 21 Grand Slam singles titles.
Nadal battled a foot injury for much of last year, ending his season in August, then contracted Covid in December, saying it left him "very sick".
But the 13-time French Open champion swept through the field last week to win a warm-up event at Melbourne Park and a revitalised Nadal could be the main threat to Djokovic.
The 2022 edition marks the 10th anniversary of the pair's epic, longest Grand Slam final in Melbourne, when Djokovic finally beat Nadal at 1:37am, after five sets and five hours and 53 minutes of exhausting play.
- Daniil Medvedev -
The 25-year-old Russian won his first major at the US Open in September when he blew away Djokovic in straight sets to end the Serb's chance of winning a calendar Grand Slam and avenge his defeat in last year's Australian Open final.
The world number two ended a highly successful 2021 in which he lifted four ATP titles by winning all five of his singles matches to lead his country to a third Davis Cup triumph in December.
The ultra-consistent Medvedev won 63 matches last year, more than any other player, and has lifted all but one of his 13 ATP titles on hard courts.
- Alexander Zverev -
The world number three won a tour-leading six tournaments in 2021, including Tokyo Olympic gold, but still needs to rid himself of the reputation of choking at the sharp end of Grand Slams.
Despite his prodigious talent the German has still only reached one Grand Slam final -- the US Open in 2020, where squandered a two-set lead to Dominic Thiem.
His best performance in Australia was two years ago when he reached the semi-final, losing in four sets to Thiem.
The 24-year-old finished off 2021 by beating Medvedev to win his second ATP Tour Finals crown.
- Stefanos Tsitsipas -
The world number four burst onto the scene at the Australian Open in 2019 when as a 20-year-old he dethroned defending champion Roger Federer in the last 16.
The Greek went on to win the ATP Tour Finals at the end of that season aged 21 to become the youngest year-end champion since Lleyton Hewitt in 2001.
As one of the flag bearers for the "Next Generation" of players looking to take over from the big three, he reached his first Grand Slam final at Roland Garros last year, losing to Djokovic.
Comes into Melbourne with a question mark over his fitness following elbow surgery at the end of last season.