Nadal and Federer treated the O2 Arena fans to some superb exchanges early on, reminiscent of the classic matches that have punctuated their nine-year rivalry. But Nadal was much sharper on the important points, converting all four break points he earned, while Federer sometimes looked like a shadow of his old self, hitting 32 unforced errors and some poor volleys.
"I struggled to stay consistent throughout the match," Federer said.
The 32-year-old Swiss, who beat Juan Martin del Potron on Saturday to qualify for the semis while Nadal had a rest day, also looked tired towards the end.
Federer missed an early chance when he failed to convert three break points in the sixth game before Nadal took advantage of his first opportunity to break for 5-4 with a superb forehand winner.
Federer sent the crowd in rapturous cheers as he broke back immediately after winning a long rally with a forehand down the line and Nadal netted a shot.
Federer could not build on the momentum and dropped his serve in the next game before Nadal closed out the set. The Swiss then struggled with his rhythm and was broken twice in the second set, with Nadal sealing the victory when Federer sent a volley long.
- AP