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 ever loss on clay at the French Open this year, powered his way through the Group B match by mixing a hard forehand with a solid backhand to keep Nadal on the move.
The second-ranked Nadal can still advance to the semi-finals of the season-ending tournament for the top eight players in the world.
Novak Djokovic was to play Nikolay Davydenko later Monday in the other Group B match.
Soderling won both sets by breaking Nadal 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 really 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.
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.
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 maiden Grand Slam final, but lost to Roger Federer.
Nadal then spent time off the court, missing out on defending his Wimbledon title because of knee injuries and later taking a second break after the U.S. Open to treat a stomach muscle.
On Tuesday, four-time champion Roger Federer will face Andy Murray in Group A. Both players won their opening matches on 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 semi-finals.