Federer nails Wawrinka to enter final

Days before Roger Federer and Stanislas Wawrinka team up for a shot at Switzerland's first Davis Cup title, they were tearing lumps out of each other at the ATP World Tour Finals in London on Saturday.

Federer spent nearly three hours fighting off Wawrinka in an intense semifinal, admitting he was fortunate to save four match points before scraping through 4-6, 7-5, 7-6 (8-6) and setting up a blockbuster season finale against Novak Djokovic.

Wawrinka's nerve failed him when serving for the match at 5-4 in the third set and Federer conceded he could easily have been the one left to contemplate a semifinal exit.

"I clearly got lucky tonight. There's no doubt about that," Federer said. "But you've got to keep believing that maybe there is a slight chance that you are going to be able to turn it around somehow.

"It's hard on Stan," the six-times Tour Finals champion added. "I think if he would have served a little bit better today he would have won."

Wawrinka was cramping up in the deciding tiebreak and both players looked out on their feet after a thrilling toe-to-toe battle.

"Hopefully he will recover from this fast enough, that would be good for both of us," Federer told reporters at almost 1 a.m. local time. "I checked on him immediately after the match to see if he was okay."

Quite what Swiss Davis Cup coach Severin Luthi would have made of it is anyone's guess and he will hope Federer does not get too bashed up by Djokovic in their 37th meeting on Sunday.

France, their opponents in the Davis Cup final, would have enjoyed the sight of Switzerland's two heavyweights digging deep into their energy reserves on Saturday night.