By Clare Lovell
LONDON (Reuters) - Roger Federer finally blotted his copybook on Wednesday, dropping a set for the first time at this year's Wimbledon before reaching the semi-finals with an emotional victory over friend and Swiss compatriot Stanislas Wawrinka.
It is the ninth Wimbledon semi-final for the 32-year-old seven-times champion, who has been in imperious form on the grass this year, winning at Halle before steaming through five rounds at the All England Club.
Federer, playing his 16th tour match against his Davis Cup team mate Wawrinka, looked listless during the first set before getting into his stride to notch his 14th win over the Australian Open champion 3-6 7-6(5) 6-4 6-4.
"It's tough (playing against a friend). Stan played great, especially in the first two sets, until he started to really struggle with his fitness," Federer said.
Wawrinka had to compete on three successive days after weekend rain caused scheduling problems at the championships. He had also spent and hour and 40 minutes longer on court than Federer.
"I just know it was tough to play three days in a row, especially when you played the third against Roger," a weary Wawrinka said. "You have to be more than 100 percent ready physically, but mentally also.
Federer said he wanted to win the match but not necessarily to beat Wawrinka.
"So that's the odd part," he said. "I still felt I was able to focus well and play as good as Stan allowed me to play, because he was playing really well right out of the gates.
"He came out and was crushing the ball, forehand and backhand and even serve, so it was very difficult for me."
Wawrinka did manage to exposed a slight chink in Federer's formidable armor, inducing a nervy final game from the 17-times grand slam champion, who required five match points to wrap up the contest.
Federer's semi-final on Friday will be against Canadian Milos Raonic, who beat 19-year-old Australian Nick Kyrgios, conqueror of world No.1 Rafael Nadal.
"He's got a big serve," Federer said of the 23-year-old Raonic. "Clearly that's what is most visible when you see him play. That's the hardest to deal with.
"Here on the grass with a serve like that it's never going to be an easy match."
But the Swiss maestro said he welcomed young players coming through in the big tournaments to challenge established top players, such as himself, Nadal, Andy Murray and Novak Djokovic.
"It's exciting for the game to see new faces like Kyrgios, now Raonic or (Kei) Nishikori, you name it. There's been a few guys knocking on the door now."
(Editing by David Goodman and Pritha Sarkar)