Resurgent Roger Federer said a long period of rest when he took six months out with injury had fuelled his incredible shot at more Grand Slam glory at the Australian Open.

The 35-year-old Swiss veteran is wowing the tennis world with his wholly unexpected run through to Sunday's final, raising the prospect of an unprecedented 18th major title.

Federer, whose ranking has dipped to 17 after a knee problem ended last season following Wimbledon, has defied the doubters by reaching his 28th Grand Slam title match.

After a fighting, five-set semi-final win over fellow Swiss Stan Wawrinka, he became the oldest man to reach a major final since Australia's Ken Rosewall (39 years 310 days) at the 1974 US Open.

Federer said much of his rejuvenation stemmed from his injury break, the longest of his career, which followed surgery on his knee earlier in the season

"It was a good thing to do. You can only ever do so much treatment to feel decent," said Federer, whose 19-year playing career has been largely injury-free.

"What I've come to realize is when you don't feel well, you have too many problems going on, you just won't beat top-10 players.

"All the time all you're doing is fighting the fire. From that standpoint, yeah, the six months definitely gave me something in return."

The Swiss marvel has spent a total of 13 hours 40 minutes on court in his six matches to get to his sixth Australian final, but he says he feels in good shape.

"I just wanted to get healthy again. I'm happy this week has been a good one," he said.

"So I will leave it all out here in Australia and (even) if I cannot walk for another five months, I will give it all I have."

- 'Just relax, man' -

Federer, a staunch tennis traditionalist, said it meant a great deal to be linked with a record set by Rosewall, an eight-time Grand Slam-winner, by reaching the final. 

"We don't speak about him enough. I think he's a wonderful man," he said.

"He wrote me a letter again this week to wish me well again. He does it every year at the Australian Open. Still haven't seen him, unfortunately. I know he's around.

"I love that generation of players with Tony Roche, Rod Laver, Ken Rosewall, Roy Emerson. 

"I know he's a few years older, but I know he had a tremendous career. So to be in the same breath like these guys, it's a great feeling.

"I love these guys. It means a lot to me to have equalled something like this since a long time."

Federer said his charge through the top half of the men's draw, aided by the shock exit of world number one Andy Murray, had surprised even him.

All the same, he needed to give himself a talking-to before completing Thursday's three-hour, 7-5, 6-3, 1-6, 4-6, 6-3 win over Wawrinka.

"It's gone much better than I thought it would. That's what I was telling myself in the fifth set," he said.

"I was saying like, just relax, man. The comeback is so great already. Let it fly off your racquet and just see what happens.

"I think that's the mindset I got to have, as well, in the finals. Sort of a nothing-to-lose mentality.

"It's been nice these last six matches to have that mentality. It worked very well so I'll keep that up."