It was a blast from the past when Roger Federer and Rafael Nadal took centre stage at the Australian Open last year. The flashback slam got the finish it deserved when Federer outlasted his good friend Nadal in a colossal five-set battle on Rod Laver Arena.
Fast forward 12 months and it is hard to envisage the two tennis greats going head-to-head again in a showdown for the ages at Melbourne Park on January 28 – and it is all because of the 31-year-old Spaniard and world number one.
Federer and Nadal's preparations for the Australian Open could not be more contrasting as the latter deals with an ongoing knee problem which continues to threaten his bid for a second Melbourne title and first since 2009, when he left the Swiss maestro weeping like a schoolboy on RLA.
A knee injury which has prevented Nadal from playing competitively since losing to David Goffin at the ATP Finals in November has restricted the 16-time major champion to just a pair of exhibition contests in Melbourne – a far cry from his run to the quarter-finals at the Brisbane International last year.
Nadal – who withdrew from the Mubadala World Tennis Championship and the Brisbane International – lost to Richard Gasquet at the Kooyong Classic on Tuesday before going down to Tomas Berdych in the Tie Break Tens tournament a day later.
What was more concerning, albeit in an exhibition, was his performance against retired 36-year-old Lleyton Hewitt in the semi-finals of the event – first to 10 points – having survived match points against the Australian.
Nadal now heads into the year's opening slam, where the top seed will kick off his campaign against Victor Estrella Burgos, with more questions than answers.
"Last year's season was a bit long and I had to start a little bit later than I would've liked. For me it was not ideal to not be in Brisbane, I would have loved to be there but I had to make a different schedule this year," Nadal said during the week.
"For the first time I have to play here at the Australian [Open] for the first tournament of the year. I'm excited about it and I've got a few days to practice."
As for Federer, it is business as usual in his pursuit of a remarkable 20th grand slam.
While Nadal and six-time Australian Open champion Novak Djokovic battle to prove their fitness following the withdrawal of five-time runner-up Andy Murray, defending champion Federer is pain-free and enjoying a relaxed build-up.
An unlikely winner at Melbourne Park in 2017 before going on to capture Wimbledon, the evergreen 36-year-old – who enjoyed a renaissance last season having been struck down by injuries in 2016 – is trusting his tried and tested preparation, having featured at the Hopman Cup in Perth just like he did last year.
There is a difference, however, with Federer guiding Switzerland to their third Hopman Cup trophy – 17 years on from claiming the title alongside Martina Hingis.
"Everybody thinks I probably have a good chance to maybe repeat and other guys are maybe a bit hurt," Federer said recently before being drawn against Aljaz Bedene in the opening round. "All these things all play into it but at the end of the day I've been in this position thankfully many times before.
"Defending a title the very first time is the hard part… if you don't win, it's all dramatic but later on in life you take it as it comes, try your best and if it works out, great but if it doesn't, it just doesn't."
The tennis community and sporting world yearns for another instalment in the Federer-Nadal rivalry but while form is temporary and class is permanent, a lack of preparation may rob the Australian public of another unforgettable event.