Djokovic exhausted ahead of Nadal clash

Robin Soderling (pic) downed Novak Djokovic to claim his second big scalp at the ATP World finals.

Novak Djokovic admits he is struggling to find the energy to take on Rafael Nadal on Friday in a match that could end his reign as ATP World Tour Finals champion.

World No.3 Djokovic cut an exhausted figure as Sweden's Robin Soderling overpowered him in the second set at London's O2 Arena on Wednesday to claim a 7-6 (7/5) 6-1 victory.

The Serb now needs to beat Australian Open champion Nadal to have any chance of making the semi-finals as he tries to defend the trophy he won for the first time in Shanghai last year.

The match will be a dead rubber for Nadal, who was sent crashing out of the competition after going down Nikolay Davydenko 6-1 7-6 (7/4) in an hour and 47 minutes on Wednesday.

Asked if he could get ready for the Nadal match, Djokovic said: "I don't know. I will see. I'm very tired. It's just fatigue of the whole year."

In his position as a member of the ATP Player Council, Djokovic has already had to debate whether it would be better for players' fitness to shorten the season.

Although the Serb seems to be suffering more than most from the daunting schedule that the ATP Tour demands of its' top stars, he refused to criticise the sport's bosses.

"I don't know (if the season is too long). I prefer not talking about it now," he said.

"I don't think I played too much. I just played very solid in all the tournaments that I was committed to play. So I played all the tournaments that I had to play."

While Djokovic can't wait for the season to finish, Soderling is having the time of his life in London.

Although he was only the first alternate for the tournament, he arrived in the English capital five days before the first match in case any of the players withdrew and was rewarded when Andy Roddick pulled out injured.

"I knew for a pretty long time that I was going to be at least first alternate here, so I prepared as if I was going to play," he said.

Ending Nadal's four-year reign as French Open champion en route to the final, where he was beaten by Roger Federer, has transformed Soderling's status on the Tour from journeyman to rising star.

The world number nine believes the key to his success has been his ability to control his fiery temper, which had often led him into costly on-court meltdowns when things didn't go his way.

"I try to work a lot on it," he said. "Of course I lost a lot of matches because of my temper. Everyone is always talking about the matches I lost, not the matches I won, because of my temper.

"But I think I have a little bit of a different approach to everything this year compared to the other years."

In the final round of Group B Soderling will play Davydenko.