Serena enters semis

American ends season as number one, faces Wozniacki next

Serena Williams reached the WTA Finals semis and was crowned year-end world number one without picking up a racquet on Friday when results went her way at the season finale in Singapore.

The four-time champion was in stark danger of crashing out but she earned a reprieve when Simona Halep, her tormentor in a crushing 6-0, 6-2 defeat earlier this week, won a set against Ana Ivanovic.

And more stars aligned for the 18-time Grand Slam-winner when world number two Maria Sharapova made an early exit — ending her chances of overtaking the American in the year’s final rankings. Caroline Wozniacki stormed past Petra Kvitova 6-2, 6-3 to set up a semifinal against Williams on Saturday, while Halep will play Agnieszka Radwanska in the last four.

Ivanovic departs despite beating Halep 7-6 (9-7), 3-6, 6-3, while Sharapova also leaves after rallying for a 7-5, 6-7 (4-7), 6-2 win over Radwanska.

Under complex round-robin calculations, Sharapova needed a straight-sets victory to survive and she came agonisingly close when she passed up three match points in the second set.

While Sharapova's season is over, Wozniacki's is still very much in play after a victory over Kvitova that left her as the only player in the tournament to win all the group matches.

Super-fit Wozniacki, who is training for next month's New York marathon, again made all the running as she beat Kvitova in 69 minutes. Following her three-hour slugfest against Sharapova and straight-sets win over Radwanska, the resurgent former world number one has hit a patch of form that has re-announced her as a force in women’s tennis.

Later Ivanovic fought bitterly for the straight-sets win over Halep that she needed to stay alive, and momentum was with her when she came from behind to win the first set on a tie-breaker.

But the former French Open champion missed an open-court volley as she was broken early in the second set, which she lost 6-3.  But like Sharapova, she gathered herself for an all-out effort in her final set of the season and she took it 6-3 to seal the win.