Wozniacki stays perfect
Top seed Caroline Wozniacki beat Slovakia's Daniela Hantuchova to preserve her unbeaten record at the Tournament of Champions in Sofia.
The Dane made it three wins from three in the round-robin stage, coming from behind to beat the seventh seed 3-6 7-6 (7/4) 6-4.
Wozniacki had already secured a place in the semi-finals following Wednesday's victory over Italian fourth seed Roberta Vinci, who beat Su-Wei Hsieh 6-1 6-2 to also progress.
In the other group, Nadia Petrova made sure of a last-four spot with a 3-6 7-6 (7/4) 6-3 victory over Russian compatriot Maria Kirilenko.
Despite the defeat, Kirilenko also qualified for the semis but was then forced to pull out of the competition through illness.
Tsvetana Pironkova will instead advance to the next round. The Bulgarian plays Petrova tomorrow to determine who will top the group.