LONDON: Russia's Nikolay Davydenko stunned Roger Federer to reach the final of the ATP World Tour Finals with a 6-2, 4-6, 7-5 victory over the world number one on Saturday.
Federer had never lost to Davydenko in 12 previous meetings, but the Wimbledon and French Open champion was unable to extend that run in the semi-finals at London's O2 Arena.
Davydenko, who will face either Juan Martin Del Potro or Robin Soderling in Sunday's final, had only qualified for the last four late on Friday and he was back on court just 14 hours later.
But the Russian showed no signs of fatigue as he booked his place in the final for the second successive year.
Federer could not take advantage of two break points early on and then played a terrible game, serving two double faults and throwing in two more unforced errors to hand Davydenko the first break.
Another double fault and a netted forehand gave Davydenko - beaten in last year's final by Novak Djokovic - a shock 4-1 lead.
The Swiss star got one of the breaks back immediately, but the respite was only temporary and Davydenko made it three breaks in a row before sealing the first set.
Federer was in danger of being blown away and he gradually found some rhythm in the second set. A series of superb winners seized the initiative and he broke at 5-4 to level the match.
He had the advantage of serving first in the decider and at 4-5 the match came alive.
A lucky net cord gave him the opening point and an outrageous shot off a Davydenko smash put Federer in sight of the final.
But he could not take his chance as Davydenko held his nerve to level at 5-5.
And the Russian capitalised fully by creating a break point in the next game, which he took with a stunning backhand return.
Two big serves took Davydenko to 30-0 but Federer was not finished, a brilliant rally resulting in a break point.
This time Davydenko blasted a forehand winner and one big serve later he was at match point, which he took when Federer netted a forehand.