Rafael Nadal again loses to Robin Soderling

 AP – Robin Soderling reacts after gaining a point, during his match against Rafael Nadal in their ATP World …

• By CHRIS LEHOURITES, AP Sports Writer
• Chris Lehourites, Ap Sports Writer – 10 mins ago

LONDON – Rafael Nadal lost to Robin Soderling for the second straight time, falling 6-4, 6-4 Monday in their opening round-robin match at the ATP World Tour Finals.

Soderling, who handed the Spaniard his first loss on clay at the French Open this year, powered his way through the Group B match by keeping Nadal on the move on the hard court at O2 Arena.

"I didn't play really bad," Nadal said. "But in the important moments, I didn't have this calm, this necessary calm, to win these matches against the best players of the world."

Novak Djokovic plays Nikolay Davydenko later in the day in the other Group B match.

The second-ranked Nadal can still reach the semifinals of the season-ending tournament for the top eight players. He can also capture the year-end No. 1 ranking from Roger Federer, but Monday's loss hasn't helped his chances.

"My level right now I think is not to be No. 1," Nadal said. "My level is to be still fighting and practicing hard to be ready as soon as possible to compete another time with equal conditions with everybody."

On Tuesday, four-time champion Federer will face Andy Murray in Group A. Both players won their opening matches Sunday. In the other match, U.S. Open champion Juan Martin del Potro will play Fernando Verdasco. The top two players in each group after the round-robin stage will advance to the semifinals.

Soderling won both sets by breaking serve in the final game. Before the end of the first set, however, Nadal had thought he won the game and evened the score at 5-5.

Serving at 40-30, Nadal allowed himself a moment of celebration when his first serve whizzed by Soderling. But before the Spaniard was able to let his emotions loose, his serve was called long.

Off the second serve, Nadal sent a forehand long, setting up deuce. Two more mistakes off the forehand gave his Swedish opponent the game and the set.

"I tried to keep on fighting, keep telling myself that I will get one more chance this set, and I took it straight away," Soderling said.

Like in the first set, Nadal and Soderling traded breaks early in the second. In the final game, Nadal saved one match point when Soderling put a forehand long, but the Spaniard shanked a backhand on the second.

Nadal finished the match with 24 unforced errors and only 18 winners, while Soderling had 27 and 23. Both had five aces.

"Sometimes you have some best moments; sometimes you have little bit worse moments. This probably is one of these moments for me right now," Nadal said. "Just accept and work to improve the situation."

Nadal had won four straight French Open titles heading into the 2009 season, but Soderling beat the then-top-ranked player in the fourth round at Roland Garros. Soderling went on to reach his first Grand Slam final, but lost to Federer.

Nadal then was unable to defend his Wimbledon title because of knee injuries. He later took a second break after the U.S. Open to treat a stomach muscle.

"The second half of the year was difficult for me," Nadal said. "But I am working really hard to come back at my best level. I think I'm not far away."

The ninth-ranked Soderling was invited to the tournament only after Andy Roddick withdrew because of injury.

"I never really thought of vacation because I know I was first alternate," Soderling said. "I tried to prepare as if I was going to play. ... I wouldn't call it a free chance. I worked pretty hard throughout the year to get this chance."