Davydenko joins fellow Russian Mikhail Youzhny in the last four

Seventh seed Davydenko looked out on his feet after dropping the first two sets, but stayed alive with a decisive break in game eight of the third set.

The Russian then levelled before edging a tense decider that saw five breaks of serve as Haas struggled physically.

Davydenko will play top seed Roger Federer in Saturday's semi-finals.

Interview: Nikolay Davydenko

Haas made a blistering start, playing his very best tennis in reeling off four straight games to win the first set.

The second was a tighter affair but again it was the German who had the edge, taking four consecutive points to seal the tie-break.

I think I was lucky Nikolay Davydenko

But Davydenko refused to give in and one break in each of the third and fourth sets helped him level the match, with Haas missing several break points in the fourth.

With both players suffering physically, the pair swapped breaks at the start of the fifth set.

Davydenko appeared to have the match wrapped up when he surged 5-2 clear but he failed to serve out at the first opportunity and slipped 15-40 down at 5-4.

But Haas, who had earlier received treatment to his thigh, could not complete a miraculous recovery as the Russian found his first serve to take his place in the last four.

"I think I was lucky," he said afterwards.

"But it was tough, I was 5-2 (up in the final set) then break point and 5-4 and I didn't know what I could do, but I am happy to be in the semi-finals."

Haas said: "My legs started to give out a bit. My body didn't feel good anymore. I couldn't do the small steps to stand well to the balls.