Rafael Nadal is among some of the game's biggest names racing the clock to make the Australian Open start line as the world's tennis elite prepare to joust for a record $60 million summer purse.
Fresh off his incredible 2017 renaissance, Roger Federer headlines the Hopman Cup in Perth when the first of five Open lead-up events gets under way on Saturday.
From Perth, via Brisbane, Sydney and Hobart, all roads lead to Melbourne Park, where 99 of the world's top 100 women and all of the top 100 men have entered the year's first grand slam event starting on January 15.
But while 36-year-old Federer should arrive refreshed and ready for his Open title defence after a soothing family holiday, many of his chief rivals remain under serious fitness clouds.
After pulling the pin one match into his World Tour Finals campaign in London last month, world No.1 Nadal continues to battle a worrying knee injury.
Runner-up to Federer in an epic five-set final in Melbourne last year before collecting his 10th French Open crown and third US Open title, 31-year-old Nadal ended 2017 as the oldest season-ending No.1 in history.
But the Spaniard's prospects of landing back-to-back majors for the first time since 2010 don't look good after the battered baseliner's decision to cancel a five-day training camp in Majorca last week.
Nadal was scheduled to sweat it out with Joao Sousa but reportedly told the Portuguese he "still isn't ready to practice".
"He called me to tell me he was not feeling well," Sousa was quoted as saying.
Nadal was scheduled to face either Kevin Anderson or Pablo Carreno Busta on Friday at the Mubadala World Tennis Championship in Abu Dhabi but has withdrawn from that event.
He will have played just one competitive match in almost two months by the time he lobs as top seed at the Brisbane International starting on New Year's Eve.
Nadal is among three of the so-called Big Five fighting to be fit for the Open.
Five-time runner-up Andy Murray hasn't played since Wimbledon and delayed his departure from Britain as he continues to struggle with a chronic hip injury.
Frustrated by his agonising run of near misses, Murray, now ranked 16th, had planned to arrive in Australia "much earlier than I have done in the past" to acclimatise.
The fact he hasn't has raised real concerns over the Scot's ability to contest the Open, let alone genuinely compete.
Like Murray, triple grand slam champion and 2014 Open winner Stan Wawrinka hasn't been sighted since Wimbledon and, adding to the concern, the Swiss withdrew from Abu Dhabi with an ongoing knee issue.
The good news for fans is Novak Djokovic is champing at the bit to return from his six-month lay-off to challenge for an unprecedented seven men's Open crown.
Djokovic also called an end to his 2017 season after a quarter-final loss at the All England Club and will arrive in Melbourne ranked 12th and not holding a grand slam trophy for the first time in seven years.
But the Serb is buoyant after a pre-Christmas training block in Monte Carlo with his new-look coaching team headed by Radek Stepanek and motivating mentor Andre Agassi.
It's not just the leading men in doubt. Two-time Open champion and former world No.1 Victoria Azarenka is also mooted for her grand slam comeback after missing the US Open while locked in a custody battle for her son Leo with her ex-partner.
But the popular Belarusian's appearance is also uncertain after she pulled out of the Auckland Classic lead-up event for "personal reasons".
There had been questions over defending champion Serena Williams following the birth of her first child in September but the American announced on Sunday she will play an exhibition match in Abu Dhabi this week.