Nadia Petrova went 3-0 in round-robin play and captured her group this week at the $750,000 Tournament of Champions.
The second-seeded Russian was perfect in the four-player Sredets Group in Sofia after coming from behind to beat eighth-seeded heavy Bulgarian crowd favorite Tsvetana Pironkova, 5-7, 6-1, 6-3, Friday on the indoor hardcourts at Armeets Arena. Pironkova (1-2), like Petrova, had already qualified for Saturday's semifinals at this season-ending event.
Petrova's semifinal opponent will be fourth-seeded Italian Roberta Vinci (2-1), while Pironkova should have her hands full with top-seeded former world No. 1 Caroline Wozniacki (3-0).
Wozniacki captured this week's four-player Serdika Group.
Also on Friday, fifth-seeded Taiwanese Su-Wei Hsieh (1-2) held off seventh- seeded Slovakian veteran Daniela Hantuchova, 6-1, 0-6, 6-4, and Swedish alternate Sofia Arvidsson (1-0) was leading sixth-seeded Zheng Jie (0-3) when the Chinese retired from their bout while trailing 1-5 in the first set due to an upper respiratory illness. Hantuchova, like Zheng, went a dismal 0-3 this week. Arvidsson replaced ill third-seeded Russian Maria Kirilenko (1-1) in the eight-woman field on Thursday.
The Tournament of Champions is the finale for the WTA's International Series, with the six highest-ranked players who have won an International title this year -- and two wild cards -- comprising an eight-woman field. The Serdika Group boasted Wozniacki, Vinci, Hsieh and Hantuchova, while the four-player Sredets Group featured Petrova, Zheng, Pironkova and Arvidsson, following Kirilenko's withdrawal.
The tournament format sees two round-robin groups play out over the first four days, with the semifinals on Saturday and the final on Sunday.