Veterans Roger Federer and Maria Sharapova head into the opening Grand Slam of 2015 next week as the form players, but there is a heady mix of youth and experience snapping at their heels.
Evergreen Swiss great Federer, 33, brought up a jaw-dropping 1,000th victory on Sunday by beating Canadian Milos Raonic to win the Brisbane International, laying down the Australian Open gauntlet to arch-rivals Novak Djokovic and Rafael Nadal.
The world number two is now aiming for a 1,007th win, which would give him the title at Melbourne Park.
"Yeah, I do believe that," Federer said when asked if he could claim a fifth Australian Open and his 18th Grand Slam.
"Then again, it's just talk. At the end of the day, I've got to do the running, I've got to do the clutch play when it matters the most."
In contrast to his flying start to 2015, world number one Djokovic's preparations were cut short by giant Croatian Ivo Karlovic in the Qatar Open quarter-finals.
It was even worse for Nadal, who suffered a shock defeat in his first match of the season in Doha to German qualifier Michael Berrer as he continues to recover from appendix surgery.
The Spaniard, a 14-time Grand Slam winner, has played few matches since Wimbledon last July but brushed off his shaky start.
"It's a big motivation to be back at my best level as quickly as possible, and that's what I am trying to do," he said.
Swiss Stan Wawrinka is the defending men's champion after his breakthrough four-set win over Nadal last year and spearheads a host of challengers, including Britain's Andy Murray and new guard Raonic and Japan's Kei Nishikori.
- Erratic Williams -
Sharapova, who has been a fixture on the tennis circuit since 2002, continues to shine with victory over Ana Ivanovic in Brisbane handing her a 34th career title.
She won her only Australian Open in 2008, beating Ivanovic in the final.
The Russian's closest rival, world number one Serena Williams, is gunning for a sixth Australian Open title but was unimpressive at the mixed-teams Hopman Cup in Perth this month.
The American, aiming for a 19th Grand Slam crown, spluttered her way through with moments of brilliance interspersed with extended periods of erratic play.
"I do feel like I am getting back into the groove, I am not moving as well as I was last year," said the American, who is the defending US Open champion but has not won the Australian Open since 2010.
"I am going to try and improve that and I know I can so but I am getting there."
Along with a revitalised Ivanovic, world number three Simona Halep of Romania is shaping as a threat after winning the warm-up Shenzhen Open on Saturday, although she pulled out of this week's Sydney International with gastroenteritis.
The dangerous Agnieszka Radwanska is another to watch, having beat Williams in Perth.
China's Li Na won the women's crown last year, battling past surprise package Dominika Cibulkova of Slovakia, but has since retired.
There is plenty of incentive to win with the prize money bumped up to a record Aus$40 million (US$32 million), with the singles winners taking home Aus$3.1 million each.
Held in the height of the southern hemisphere summer, weather is always a wildcard in Melbourne with temperatures known to fluctuate up to 20 Celsius from one day to the next.
Last year, extreme heat forced organisers to suspend play for several hours following days of complaints about "inhumane" conditions which left some players fainting and vomiting.
At the time Murray warned organisers were risking a tragedy as temperatures hit 42 Celsius (107.6 Fahrenheit), while Canada's Frank Dancevic said he hallucinated a vision of cartoon dog Snoopy before blacking out.
Temperatures for the opening day on Monday are forecast to be a mild 21 Celsius.
The impact of the weather will be minimised this year with the installation of a third retractable roof at Melbourne Park. The Rod Laver and Hisense Arenas already had this facility and Margaret Court Arena has now joined them.
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