Aussie tennis great Pat Cash believes Roger Federer is eyeing off one more incredible feat before he retires.
Federer's successful Australian Open title defence has left the 36-year-old with the chance to supplant Rafael Nadal from top spot in the world rankings.
He now faces a big decision whether or not to contest the Dubai Open, starting on February 27, where a title would make him the oldest men's world No.1 in tennis history.
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And 1987 Wimbledon champion Pat Cash reckons that's Federer's ultimate goal.
"I think there's probably one last thing that he'd really like to do," Cash told Eurosport.
"That is to be the oldest world No.1. I know that for a fact that he wants to be the oldest No.1.
"He had to defend his title to get that, of course, he's got some other big titles coming up. Miami, Indian Wells, Wimbledon of course where he's always going to be the favourite.
"Rafa's just got to drop off, which he has, so he's going to edge closer to that.
"I think that will always be 'Well, I've done everything now'."
The Swiss superstar is carefully weighing up his 2018 schedule and not ruling out playing the claycourt season - possibly for one last time - after skipping the French Open last year to focus on Wimbledon.
Federer suffered a surprise second-round loss to world No.116 Evgeny Donskoy in Dubai last year, leaving him with precious few rankings points to defend if he returns next month.
Nadal said after retiring from his Australian Open quarter-final against Marin Cilic that he hoped to make his comeback from a hip injury on the Acapulco clay the same day as the Dubai event starts.
But, regardless, the Spaniard will have no say in the No.1 matter if Federer plays - and reigns - in Dubai after failing to defend the points he amassed in making last year's Open final in Melbourne.
Federer will spend the next fortnight celebrating his record-equalling sixth Open triumph with family and friends in Switzerland and won't be rushed into committing to an appearance in the Middle East.
"We were in talks with them but when the (Australian Open) tournament started, I just said: 'Look, if it's OK, I'd like to decide after the tournament'," Federer said on Monday.
"That's an ideal scenario for me and my family. After the tournament, I'll know how I feel ... did I come out injured or not?
"So now we know what the situation is.
"I also have to decide on the claycourt season so all these things are kind of interlinked.
"But it's possible I'll play something, but it's also possible that maybe I just don't play anything (for a while)."
Federer hadn't successfully defended a grand slam crown since the 2008 US Open, while his latest victory at Melbourne Park came 14 years after his first.
Andre Agassi holds the record as men's tennis's oldest world No.1, the American last holding down top spot at 33 years and four months in 2003.
Federer would be almost six months shy of his 37th birthday if he won Dubai and scaled the summit for the first time since November, 2012.