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 -
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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.
