Federer held off a thrilling fightback from Stan Wawrinka to win their semi-final 7-5 6-3 1-6 4-6 6-3 on Rod Laver Arena but had to call a medical time-out at the end of the fourth set.
The Swiss said afterwards he had been suffering from a minor problem with his upper leg in Melbourne and that it had caused him some discomfort against Wawrinka from the second game onwards.
Federer did not look too seriously troubled and he also has two full days to recover for the final. Asked if the injury would affect him this weekend, Federer said: “If I had to say anything right now, no.
“The leg wasn’t better or worse in the fifth. I felt tightness throughout the match and I felt like it slowed me down.
“I just hoped that maybe having the physio work on it, that it would make me feel better but it didn’t. It’s not something I’m necessarily really worried about in any way. So that’s a good thing.”
Federer is through to his 28th grand slam final, where he is bidding to claim a fifth Australian Open crown and a first major title in four a half years having collected number 17 at Wimbledon in 2012.
At 35, he is the oldest man to reach a grand slam final since the 39-year-old Ken Rosewall made it to the last hurdle at the US Open in 1974.
His progress is all the more remarkable given Federer arrived in Melbourne without a single ATP Tour match under his belt in more than six months, having taken the second half of 2016 off to recover from injury.
“Now it seems like it was a good thing to do,” Federer said.
“What I’ve just come to realise is when you don’t feel well, you have too many problems going on, you just won’t beat top-10 players.
“At some point you reach a limit, and you just can’t go beyond that. You can play them tight. You might win one of them. You just can’t win back to back.
“That’s where both, I guess, Rafa and myself said, ‘Okay, enough of this already. Let’s get back to 100%, enjoy tennis again, enjoy the practice. Not just practice, treatment, practice, treatment, match, treatment’.
“All the time all you’re doing is fighting the fire. From that standpoint, yeah the six months definitely gave me something in return.”
Wawrinka’s miserable record against Federer now extends to 19 defeats in 22 career meetings and he has never beaten his compatriot on a surface other than clay.
“I’m really sad and disappointed with a loss like that because to be that close to have won a semi-final, it can be only sad,” Wawrinka said.
“At the end I had a great battle against Roger. He’s a great fighter. He’s always been amazing in grand slams, in five-set matches. I’m for sure sad to lose a match like that.”
“I think the fact that he was out for six months also, fans and people in general missed him on the tour. So the fact that he come back, that he’s playing, for sure,” Wawrinka said.
“Everyone wants even more to see him play, to see him win... He’s flying on the court. He’s playing amazing tennis. He’s the best player ever.”