Few players could better understand Carlos Alcaraz's frustrating pursuit of a career grand slam better than Roger Federer.
The Australian Open is the only major to have eluded Alcaraz, who has won the French Open, Wimbledon and US Open twice and had all three of those slams in his pocket by 2024.
Alcaraz, 22, has never made it past the quarter-finals at Melbourne Park, where arch-rival and defending champion Jannik Sinner, 24, has won twice.
Federer famously was unable to claim his first and only Roland Garros title - amid Rafael Nadal's dominance on clay - until 2009, a full five years after he'd won the other three slams.
He indicated no-one would be more aware of the gap missing from Alcaraz's resume than the man himself.
"He knows about it. It's like Rory (McIlroy) going for the Masters, you know, those things are tough," Federer said.
"But at the end of the day his momentum shifts towards the first round and then it's point for point mentality. That's what it is.
"But it's true, at his young age, to be able to complete the calendar or career grand slam already now, I mean, would be crazy." added Federer.
"So let's see if he is able to do crazy this week and I hope he does because for the game, again, that would be an unbelievable special moment.
"But he has another hundred and whatever players that say like, 'we don't agree with those plans.' So they'll try everything to stop him."
Six-time Open champion Federer's rivalries with Novak Djokovic and Nadal, who also completed career slams, were the stuff of legend.
But he is relishing watching Sinner - who is only yet to win a French Open - and Alcaraz carve out their own place in history, and highlighted the Spaniard's incredible five-set comeback win at Roland Garros last year.
The pair have won the past eight slams between them.
"The rivalry between Alcaraz and Sinner, I think, is a great one. I mean, they play incredible tennis," Federer said.
"That French Open final was unreal. I think the game, not that it needed it, but I think it was great that we had it.
"Because I feel like for a second, for a moment, the world stood still in the sporting world and watched towards Paris and what was going on in that epic fifth set.
"Because it could have ended much, much sooner for Jannik, obviously and then all of a sudden, it just ended up in this most crazy fashion, maybe one of the greatest games we've ever had in our sport.
"So I think it's good we still live off that momentum and then they backed it up by playing each other in all those other finals and everybody else is trying to keep up and they're still trying to pull away.
"Because what we've seen in terms of their progression in the last years, it's been wonderful. I practiced with both guys a little bit and they're incredible ball strikers and there's obviously more to come."
Alcaraz kicks off his tournament against Australian Adam Walton while world No.2 Sinner plays Frenchman Hugo Garcia first-up.
Retired great Federer is back in Australia for the first time since his final Open appearance in 2020 and will headline the tournament's inaugural opening ceremony.
