Federer in straight-set victory over Tipsarevic

Roger Federer opened his quest for a seventh season-ending title by beating Janko Tipsarevic 6-3, 6-1 on Tuesday at the ATP finals.

The 17-time Grand Slam champion lost only eight points on his serve while converting four of his nine break points.

In the other Group B match, David Ferrer was to face Juan Martin del Potro later Tuesday at the O2 Arena.

The season-ending tournament features the top eight players in the world. Fourth-ranked Rafael Nadal is missing because of injuries.