Nikolay Davydenko hailed the best win of his career after finally beating Roger Federer at the 13th time of asking to reach the final of the Barclays ATP World Tour finals.

The Russian, who also reached the final last year before losing to Novak Djokovic, held his nerve in the decider to come through 6-2 4-6 7-5.

Davydenko, who will play Juan Martin Del Potro in Sunday's final, said: "I think all my family, everybody who supports me, have waited for this moment because I beat everyone in top 10 except Federer. It's a really good feeling.

"I don't think now I'm number one because I beat Federer, but I know now, if I come to a match and play against number one, number two, number three in the world, I have a chance.

"That's really good confidence for next year."

As well as having the weight of history against him, the schedule was also unkind to Davydenko, with the sixth seed given less than 16 hours to recover after his three-set win over Soderling last night.

"I was tired, really tired," he added. "Between yesterday and today I was feeling like I was moving a little bit slow.

"We'll see tomorrow. Now I have a little bit more time. I want to recover 100 per cent. I hope tomorrow I will be fit for the final."

After winning the first six points, Federer played one of the worst sets of his career as Davydenko raced ahead.

The world number one fought back to level but there were only fleeting glimpses of his brilliant best.

One of those came with his opponent serving to stay in the match at 4-5. A lucky net cord gave Federer the first point before an outrageous shot off a Davydenko smash took him within sight of victory.

Davydenko held his nerve, though, and promptly secured a break of his own before coming through a tough game to clinch victory.

Describing his emotions in that crucial game, Davydenko said: "I was thinking, Federer is lucky again.

"In 12 matches he beat me. I was thinking 'Not again, please'. But then I have better concentration. Then I start to be lucky."

Federer was looking to reach the final for the sixth time after winning four out of five successive finals between 2003 and 2007.

But he lost the opening set for the fourth consecutive match and admitted that ultimately proved crucial.

He said: "It's disappointing, not to lose against him, just to lose in the semis.

"Coming so far in a ough group, in a tough tournament, I had hoped to get through to the final and maybe win again.

"But I missed the start again and I guess that's what cost me the match in the end. I tried everything to have a good start but I wasn't able to do it again.

"Second set it was more a story of just trying to hang on, get through to the third. As the match wore on, I actually started to feel better and better.

"I was a couple of points away but just couldn't get it done. He did well. I thought he playe strong throughout, even though I don't think it was our best match we ever played against each other."