Federer reached a record seventh Australian Open final after Hyeon Chung retired in the second set of their semi-final with blisters.

Federer, 36, faces Marin Cilic in the final on Sunday as the hot favourite to win his 20th Grand Slam.

Eurosport pundit Rusedski lauded Federer and says only Nadal has been able to take find - and take advantage - of flaws in his game.

He said: "It took him a little longer to win his first Grand Slam at 23 years of age.

"If you look at the past greats, they always won their first Slams a little bit sooner.

"He just has so much variety. When you have too much, sometimes you're confused because you don't know what to do out there and how to use all the strengths in your game.

"It's like 'how do I win, how do I set up points?'

"He's got the luxury is that physically, I don't think there's been a tennis player, maybe Bjorn Borg, who has been such a great athlete in the men's game.

"On top of that there's no real weaknesses in Federer's game.

"Yes, the backhand up high was a small weakness which Nadal took advantage of, but if you look at everything, it's flawless perfection."

Federer led 6-1 5-2 when 21-year-old Chung was forced to quit after having treatment on his left foot.

Nadal, meanwhile, had to pull out the tournament himself having struggled with a leg injury during his quarter-final clash with Marin Cilic.