Former world No. 1 Caroline Wozniacki went 3-0 in her round-robin matches this week and will play in Saturday's semifinals at the $750,000 Tournament of Champions.

The top-seeded Danish star overcame seventh-seeded Slovakian veteran Daniela Hantuchova 3-6, 7-6 (7-4), 6-4 on the indoor hardcourts at Armeets Arena. The winless Hantuchova is 0-2 in round-robin play heading into Friday.

Wozniacki captured this week's four-player Serdika Group.

"I played solid and served very well. I am pleased with my performance," Wozniacki said.

Meanwhile, second-seeded Nadia Petrova moved to 2-0 with a 3-6, 7-6 (7-4), 6-3 comeback victory against ailing third-seeded fellow Russian Maria Kirilenko (1-1) and fourth-seeded Italian Roberta Vinci (2-1) pasted fifth-seeded Taiwanese Su-Wei Hsieh 6-1, 6-2 in 53 minutes in the Day-3 nightcap to join Wozniacki in the final four.

Kirilenko promptly pulled out of the field after losing to Petrova, citing an upper respiratory illness.

On Friday in Sofia, Petrova will take on eighth-seeded Bulgarian crowd favorite Tsvetana Pironkova (1-1), Hsieh (0-2) will meet Hantuchova, and sixth-seeded Chinese Zheng Jie (0-2) will face Swedish alternate Sofia Arvidsson, who replaces Kirilenko in the Sredets Group. Petrova and Pironkova, like Wozniacki and Vinci, have also qualified for the semifinals and the winner on Friday will capture the Sredets Group.

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 aforementioned Serdika Group boasts Wozniacki, Vinci, Hsieh and Hantuchova, while the four-player Sredets Group now features Petrova, Zheng, Pironkova and Arvidsson (0-0), 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.