Rafael Nadal may have had enough injury trouble this season, but it’s his mental attitude that needs sorted if he is to mount any sort of serious challenge at this year’s World Tour Finals.

The Spaniard lost his opening game of the round-robin phase at the season-ending showpiece in London 6-4, 6-4 to Robin Soderling.

It was the second time the Swede had toppled Nadal this year after shocking the left-hander at the French Open in May. And after insisting he was fully recovered from recent injury problems, the World No.2 blamed his defeat not on a lack of fitness, but rather a lack of confidence.

“The second half of the year was difficult for me, and probably I lost a little bit of this necessary confidence and calm,” Nadal said.

“But I am working really hard to come back at my best level.

“I think I’m not far away.

But I need a little bit more confidence and more calm.

“This year is going to be extremely hard to finish really well.

But I’m going to work very hard to start next year very good. I believe in myself, that I can come back playing really well next year.”

Facing a showdown with Russian Nikolay Davydenko today, Nadal was keen to concentrate on the positives from the loss to Soderling - who is only playing at London’s O2 Arena as a replacement for the injured US star Andy Roddick.

“I think I didn’t play really bad, I played OK,” he said.

“But in the important moments I didn’t have the necessary calm - I played shorter in the important moments. That’s the reason he beat me.

“He’s a big player on this surface, so it’s difficult.

“If you are not completely calm and playing very well in that moment, it’s really difficult to win, and I didn’t play in this way at that moment.”

And the reigning Australian Open champion admitted he was now unlikely to overtake Switzerland’s Roger Federer at the top of the rankings.

“My level right now is not to be number one,” the Mallorcan said.

“My level is to be still fighting and practicing hard to be ready as soon as possible to compete another time. Going on the court, with the full confidence in myself against everybody.”

Surprise package Soderling earlier this year became the only man ever to beat Nadal at Roland Garros. The Swede, who broke the clay king’s incredible 31-match winning streak in Paris, was delighted with the win. Soderling said: “It feels better to beat the world No.2 than the world No.200. I always enjoy beating good players rather than lower-ranked players.”