LONDON — Robin Soderling advanced to the semifinals of the ATP World Tour Finals by beating Novak Djokovic 7-6 (5), 6-1 Wednesday for his second straight win at the season-ending tournament.

The Swede outlasted Djokovic in a tense opening set despite wasting three straight set points with the third-ranked Serb serving at 5-4. Djokovic put up little resistance in the second and was broken three straight times, netting a forehand on Soderling's second match point.

Soderling entered the tournament as an alternate after Andy Roddick pulled out with a knee injury. He also beat Rafael Nadal in straight sets Monday in a rematch of their French Open encounter. He is the first player to reach the semifinals at the tournament for the top eight players in the world.

The loss ended Djokovic's 11-match winning streak, his first defeat against Soderling in six meetings. Djokovic stopped Nikolay Davydenko in his first group match and can still advance to the semifinals.

Nadal was to play Davydenko later Wednesday.

Soderling started with an ace on the first point and let his strong serve carry him throughout the match. He was never broken and finished with 10 aces.

Djokovic had his only two break point opportunities when leading 15-40 at 1-1 in the first set, but Soderling recovered with three straight service winners followed by an ace.

The Swede then led 0-40 at 5-4 but missed a number of shots to keep Djokovic in the set. In the tiebreaker, Soderling took a 6-4 lead with a forehand volley and converted his fifth set point with a service winner.

He won the last six games of the second as Djokovic grew increasingly frustrated and error-prone. Djokovic likely needs to beat Nadal to reach the semifinals.