Rafael Nadal is determined to rediscover the form that made him the world's most feared player after crashing out of the Barclays ATP World Tour Finals.

The Spaniard became the first player to be eliminated from the lucrative end-of-season tournament after a 6-1 7-6 (7/4) defeat by an inspired Nikolay Davydenko, which followed on from a 6-4 6-4 loss to Robin Soderling on Monday.

Nadal, who has struggled with injury this season and relinquished the world number one spot to Roger Federer, said: "I didn't arrive at this tournament with the full confidence that you need to win these matches. And in the moments that I had to play well, I didn't play well. I made mistakes.

"I fought a lot. Both matches I fought. I tried my best all the time, but it wasn't enough to win these matches.

"Today I think mentally I was better. That's the important thing that I improved a little bit today. Every day I'm trying a little bit more. I am ready to practise hard. I have motivation to play another time my best tennis.

"I think without playing very good tennis in all the matches, I had my chances against the best players of the world."

Nadal was simply blown away in the first set as Davydenko, aided by some passive play and poor movement by his opponent, fired down a succession of winners.

An enthralling second set saw the Spaniard display something of the form that allowed him to dominate the first five months of the season as he twice fought back from a break down.

But Davydenko simply would not give in and he came through a sensational tie-break, clinching a deserved victory in fitting style with another winner.

Davydenko, who lost to Novak Djokovic in last year's final and again in his opener on Monday, was reluctant to celebrate with qualification still up in the air but was pleased with his display.

"It's not like I won the tournament," he said. "Still, maybe there's a chance, maybe not, to come to the semi-final. But, after the first match, I show my good tennis in the second match. We'll see if I can show the same tennis in the third match."

The Russian, who revealed he is struggling with an injury to his left leg, felt the conditions suited him rather than his opponent, saying: "Today the surface was faster. That was good for me.

"That's why I won the first set easy. It's very difficult (for him) to run (for balls) if you play fast, right, left."

Meanwhile, Soderling declared there is more to come after his 7-6 (7/5) 6-1 victory over a weary Djokovic today ensured he became the first player through to the last four.

The Swede only qualified for the tournament as a reserve after Andy Roddick pulled out injured last week but he has more than proved his credentials with straight-sets victories over the Group B favourites.

Reflecting on his achievement, the 25-year-old said: "It's great. The top eight, top nine guys in the world are here. I won two matches in straight sets against the world number two and number three. I couldn't have asked for anything more."

A tight first set today finally went the way of the Swede in a tie-break after Djokovic had saved three set points in the 10th game.

Having begun slowly, Soderling improved throughout the match, with his huge groundstrokes backing up a fearsome serve, and an out-of-sorts Djokovic had no answer in the second set.

After winning the first game, the Serb, who admitted after his lengthy battle with Davydenko on Monday that he is running on empty, did not get a look in and Soderling wrapped up victory on his second match point when Djokovic dumped a tame volley into the net.

A downbeat world number three, who must now defeat Nadal on Friday and hope Davydenko does not beat Soderling if he is to reach the last four, gave credit to his opponent and believes the Swede is showing the best form out of the eight players.

"He has nothing to lose," said Djokovic. "It's his first (World Tour Finals). He won four straight sets and absolutely deserved to qualify for the semi-finals.

"I think he's the best player so far in the tournament."