Seventeen-time Grand Slam winner Roger Federer says he did not believe he would reach the Australian Open semi-finals after a six-month injury lay-off.
The four-time champion in Melbourne is making his competitive return after last playing at Wimbledon in July.
Federer beat Mischa Zverev 6-1 7-5 6-2 to set up Thursday’s last-four match against fellow Swiss Stan Wawrinka.
“Feeling as good as I am, playing as good as I am, that’s a huge surprise to me,” said the 35-year-old.
“If someone would have told me I’d play in the semis against Stan, never would I have called that one.
“For Stan, yes, but not for me. I honestly didn’t even know a few days ago that he was in my section of the draw or I’m in his section.”
Federer, who has not won a Grand Slam title since triumphing at Wimbledon in 2012, had been sidelined by a knee injury throughout the second half of last year and has slipped from third in the world to 17th.
He played in the non-ranking Hopman Cup in Perth earlier in January, but has come through 18 sets in Melbourne.
“I think winning back-to-back matches in best-of-five sets against quality, great players has surprised me most,” he said.
“Really that’s been for me the big question mark, if I could do that so early in my comeback.
“I felt I was always going to be dangerous on any given day in a match situation. But obviously as the tournament would progress, maybe I would fade away with energy, you know, that kind of stuff.