Nov. 23 (Bloomberg) -- Robin Soderling, the Swede who ended Rafael Nadal’s unbeaten run at the French Open, defeated the Spaniard for a second time this year at the ATP World Tour Finals.

The 25-year-old beat the Spaniard 6-4, 6-4 today in a group-stage match on the second day of tennis’s end-of-season tournament in the O2 arena in London.

“I was very nervous, but I got off to a great start, winning the first three games, and that helped,” Soderling said in a court-side interview after a backhand error by Nadal handed him the match.

“I played very well on the important points today,” Soderling said. “It’s a long way to go, but it’s a good start to beat the world No. 2.”

After ending Nadal’s unbeaten streak of 31 matches and four titles in the fourth round of the French Open, Soderling lost to top-ranked Roger Federer in the final at Roland Garros.

The Swede broke into the top 10 in October and entered his first ATP World Tour Finals as an alternate only last week after former U.S. Open champion Andy Roddick pulled out with an injury. Nadal, who missed the defense of his Wimbledon title mid-season because of knee tendinitis, is a two-time semifinalist at the Tour finals.

Under Pressure

Using his flat forehand, Soderling put Nadal under pressure from the beginning, moving the six-time Grand Slam champion around the medium-paced court and attacking his forehand. Two consecutive forehand errors on Nadal’s serve handed Soderling the first set 6-4.

In the second set, Nadal thumped his chest as he broke serve for 2-1. The Swede immediately got the break back, as the crowd cheered for the Majorcan. Nadal continued to struggle with his ground strokes, uncharacteristically producing more unforced errors, 24, than winners, 18.

Nadal will next play the loser of tonight’s match between defending champion Novak Djokovic and Russia’s Nikolay Davydenko. The Serb, ranked No. 3, has been the most in-form player in the run-up to the London finals, winning back-to-back tournaments in Basel, Switzerland, and Paris.

Four-time champion Roger Federer and hometown favorite Andy Murray were both tested before winning their opening group matches yesterday.

Federer fought back to beat Fernando Verdasco of Spain 4-6, 7-5, 6-1, while Britain’s Murray had opened the event by defeating U.S. Open champion Juan Martin del Potro 6-3, 3-6, 6- 2.

To contact the reporter on this story: Danielle Rossingh at the O2 arena through the London sports desk at drossingh@bloomberg.net

Last Updated: November 23, 2009 12:03 EST