NOVAK DJOKOVIC, 31 (SRB)
World ranking: 1
Grand Slams: 14
Best Australian Open result: Champion (six times)
The Serb looms over Melbourne Park for the year's opening Grand Slam as the tournament favourite. Together with Swiss Roger Federer, the duo have won eight of the nine Australian Open titles since 2010.
While both have six titles each, and are seeking to break a three-way tie for the most victories with Australian Roy Emerson, Djokovic's upturn in form last year, winning the past two Grand Slams, means he will be the man to beat.
Biggest weapon: His trademark deep returns keep opponents pegged back and his fitness levels mean he thrives in adverse conditions where others wilt.
Biggest weakness: His serve is not the fastest and his break-point conversion rate has dropped in the past year to 39.8 per cent.
RAFAEL NADAL, 32 (ESP)
World ranking: 2
Grand Slams: 17
Best Australian Open result: Champion (2009)
Biggest weapon: Nadal's whipped top-spin forehand remains one of the most vicious shots in tennis.
Biggest weakness: Match fitness is a real concern after the Spaniard pulled out of last week's Brisbane International with a leg injury. It is apparent that hard courts are putting undue stress on his body.
ALEXANDER ZVEREV, 21 (GER)
World ranking: 4
Grand Slams: 0
Best Australian Open result: 3rd round (2018)
Zverev is now firmly ensconced in the world's top five after winning the ATP Finals title in November.
Although considered the best bet to emerge as a new champion at the Australian Open, the towering talent has to prove he has the temperament for the biggest stage, having only reached one Grand Slam quarter-final in 14 attempts.
Biggest weapon: For a player who is 1.98m, his movement, agility and balance is exceptional. He has all the offensive weapons in his locker, most notably a serve that reached speeds of up to 230kmh in London.
Biggest weakness: Question marks remain over his big-game mentality despite his ATP Finals breakthrough. He simply has to improve his woeful record in Majors.
REUTERS, THE TIMES, LONDON