As the first grand slam event on the tennis calendar, the Australian Open is traditionally a time of new beginnings, although this year there is an inescapable sense of something ending too.
Should they all make it to the start line, there is a distinct possibility that this will be the last time the Big Four of the men's game all compete at the same slam.
Novak Djokovic, Roger Federer, Rafael Nadal and Andy Murray have all entered the twilight of their careers, with the burden of injuries an all-too-great reality for some of them. If any were to pull out in the days leading up to next week's tournament, it may be that we have already witnessed the last slam of the Big Four.
For now, they remain in the draw, despite some setbacks in their preparations for Melbourne. Rafael Nadal put a brave face on his current condition this week despite not having played a competitive match since the US Open in September, when he was forced to retire during his semi-final with Juan Martin del Potro due to pain in his troublesome knees.
An abdominal injury and ankle surgery followed, and the Spaniard has not played a regular tournament since. He had planned to return to the court at the Brisbane International last week, but was forced to pull out on doctors' advice after a scan revealed a thigh strain that threatened to rule him out for another month or more.
Yet he played two short-form matches at the Fast4 event on Monday and declared himself pain-free again. That feels a fragile state for the 31-year-old, who was able to reclaim the world No1 spot last year after winning an 11th French Open title but on whom injuries have taken their toll in recent years.
Andy Murray's future is also uncertain as he too struggles to balance the demands of tennis with his ailing body.
The Scot, 31, was emotional in the wake of his first-round win at Brisbane, admitting he didn't know how long he could continue to play after a difficult 18 month recuperation from injury.
“I want to try and enjoy it as much as I can and just try and enjoy playing tennis as long as I can,” Murray said. “I don't know how much longer it's going to last but we'll see.”
Following surgery on his hip, Murray played in just six tournaments during 2018 and slipped to No240 in the world.
He crashed out of the tournament in Brisbane in the second round after losing 5-7, 2-6 to 22-year-old Russian Daniil Medvedev, adding to doubts that he will ever scale the heights that brought him three grand slam titles, but for the time being is still slated to compete next week, albeit unseeded.
End of an era
Djokovic, 31, is in perhaps the best shape of the Big Four at the moment, having rediscovered some of his best form last year and returned to world No1 after claiming victory at both Wimbledon and the US Open.
Meanwhile, Roger Federer continues to defy all the odds at 37 years old. The world No3 has won the last two Australian Opens, with the 2017 triumph ending a grand slam drought of almost five years.
The men's game's most decorated player bounced back despite being widely written off, but must surely now be entering the final chapter of his playing career.
As the quartet who have virtually monopolised the biggest prizes for more than a decade come to the end of their reign, it is difficult to see who in world tennis can step up and reach that same level of dominance.
Stan Warwrinka, Marin Cilic and Del Potro are the only other male players to have won grand slam titles in 14 years, but they have never hit the heights of the other four.
Who will step up?
Alexander Zverev has been labelled the next big talent and the 21-year-old beat Djokovic to win the ATP World Tour finals in November. He is yet to do it at a grand slam, however.
For the domestic scene, the prospect of losing Murray is even more daunting with current British No1 Kyle Edmund yet to show he can deliver on the biggest occasions.
Edmund has climbed up the rankings impressively to No14 in the world but, like Murray, was knocked out of the Brisbane International in the second round after a shock defeat to Japan's world No185 Yasutaka Uchiyama and the 24-year-old is expected to be fit following a knee injury.
Whether they play or not, if all of the Big Four are unable to reach the grand slam without the shadow of serious injury concerns then perhaps we have already moved beyond the end of an era.