The possibility of a dream Australian Open decider between Roger Federer and old adversary Rafael Nadal remains alive after the Swiss maestro edged countryman Stan Wawrinka in a thrilling semi-final on Thursday night.

Making a return to elite tennis after six months out following knee surgery, Federer finally put Wawrinka to the sword 7-5 6-3 1-6 4-6 6-3 on Rod Laver Arena, becoming the oldest man to make a grand slam final since 39-year-old Ken Rosewall in 1974.

Chasing his elusive 18th major title, the 35-year-old will face either Nadal or Bulgarian 15th seed Grigor Dimitrov in the final, with that pair to square off on Friday night.

Federer has never lost to Dimitrov while he has a losing record against Nadal.

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"You would probably think I have a slight better chance to beat Dimitrov than Nadal," Federer said.


"I'm in the finals, I know that. I know I will have a chance to win on Sunday and that's a great position to be in.

"Regardless of who it's going to be against, I think it's going to be special either way. One is going to go for his first slam or it's the epic battle with Rafa."

Federer looked like he would wrap up the match in straight sets and march into his 28th grand slam final - including six in Melbourne - when he was up by two sets and with Wawrinka walking off the court almost in tears to have his knee strapped.

Wawrinka's frustration showed after going down a break midway through the second set when the fourth seed snapped his racquet over his knee, earning a code violation.

But Wawrinka, who won the 2014 title at Melbourne Park, returned for the third set from the injury time-out a driven man.

The US Open champion won 20 of a possible 26 points to crush Federer 6-1 and take the early break in the fourth.

Federer levelled but Wawrinka wouldn't be denied when he had another three break points at 4-4 before he served out the set.

Federer left the court before the start of the fifth set for his own injury time-out after suffering tightness in his leg, although he later admitted he used it to clear his head.

With a break point hanging over Wawrinka's head, a double fault gifted Federer a crucial fifth set break and he then served out the match to love.

"Always against Stan, it was always never going to be easy," Federer said.

"Especially how the third and fourth set went by, I needed to react really, because he had the upper hand from the baseline.

"I thought it was going to be tough in the fifth and I think he gave me a cheap break in the fifth.

"After that, I never looked back and I could not be happier right now."

Federer last lifted a grand slam trophy at Wimbledon in 2012 while he hasn't won at Melbourne Park since 2010.

His victory continued an extraordinary retro vibe at the tournament, with the Williams sisters, Serena and Venus, also back in the title decider at Melbourne Park for the first time since 2003.