Rod Laver is urging sports fans to savour Roger Federer while they can, with the Swiss marvel admitting he has "no idea" how long he can continuing defying father time after adding to his legend with a record-equalling sixth Australian Open triumph.
Federer can't believe he's the first man in tennis history to capture 20 grand slam singles crowns after his emotion-fuelled 6-2 6-7 (5-7) 6-3 3-6 6-1 victory over Marin Cilic in the Melbourne Park final.
"It's surreal," he said on Monday.
Federer remains hungry for more but, turning 37 in August, the father of four is offering no promises because even he doesn't know what's around the corner.
"Honest, I don't know. I have no idea," Federer said after becoming the oldest Open champion in 46 years.
"I've won three slams now in 12 months. I can't believe it myself.
"I've just got to keep a good schedule, stay hungry, then maybe good things can happen.
"Then I don't think age is an issue, per se. It's just a number.
"But I need to be very careful in my planning, really decide beforehand what are my goals, what are my priorities.
"I think that's what's going to dictate how successful I will be."
While predicting "exciting times ahead" and declaring he "would love to come back" to once again try to defend his Australian Open title in 2019, Federer said the fanciful prospect of matching Margaret Court's record 24 grand slam singles triumphs had never entered his head.
"I didn't think 20 was ever possible, to be honest. But, no, I think it's too far," he said.
"Those numbers are surreal. They're amazing. I'm very happy if it stays at 20. What a moment."
Laver - one of the Swiss's biggest fans - suspects Federer has a window of 12 to 18 months to add to his grand slam tally.
But he believes it's more important for fans to cherish the once-in-a-lifetime talent while they can, regardless if there's any more spoils for Federer to come.
"An injury can just immediately change his whole philosophy, Laver told AAP.
The only player to achieve two calendar-year grand slam sweeps says it's possible Federer will win another Wimbledon crown, and maybe a US Open.
But he can't see the "best player of all time" matching even the open-era record 23 singles slams of Serena Williams, let alone challenging Court's benchmark.
"Serena's probably going to continue making more. The quality of competition (on the men's side) is just so different," Laver said.
"You look at all the players now. They're six foot six (198cm) with huge serves. They're a tough crew to play.
"I think he's going to pick the right places to play this year and maybe a little of next year would be about all you could think that he could say: 'Okay, I could win possibly win Wimbledon, another US Open or another grand slam'."
Amazingly, Federer won his 20th slam in the 200th major of the 50-year open era on Sunday night.
In addition to owning 10 per cent of professional grand slam singles trophies, the 36-year-old has lost just one of his past 26 matches at the majors since hobbling off Wimbledon's centre court 18 months ago with a career-threatening knee injury.
He could now return to world No.1 with victory in his next event.