Murray dispatched Gilles Simon 6-4, 6-2, improved to 2-0 in Red Group round-robin play and assured himself a berth in Saturday's semifinals of the season-ending tournament.

Murray broke Simon's serve three times and won nearly half the return points in the solid victory.

Federer was a 7-6 (7-4), 6-4 winner over Radek Stepanek on Wednesday. About the only misstep Federer had was when he was leading 5-3 in the second set and Stepanek broke in a very quick game. But Federer answered with his second consecutive service break and put the match away.

Simon would seem to have the advantage for the Red Group's second semifinal spot. He beat Federer, the tournament's top-seed and two-time defending champion, in his first round-robin match and goes against Stepanek on Friday. Federer is paired against Murray.

Stepanek was called upon Wednesday to take the place of Andy Roddick, who withdrew with an ankle injury.

Round-robin play wraps up Thursday for the Gold Group. Third-ranked Novak Djokovic (2-0) has locked up one semifinal spot and will play Jo-Wilfried Tsongas (0-2). Nikolay Davydenko and Juan Martin del Potro, both 1-1, meet with the group's other semifinal berth at stake.