Petrova, Ivanovic win in upsets in Bali

Nadia Petrova and defending champion Ana Ivanovic posted upsets Thursday in quarterfinals of the WTA\'s Commonwealth Bank Tournament of Champions in Indonesia. Petrova knocked off second-seeded Peng Shuai 6-4, 6-3 with seven breaks in 10 receiving games. Petrova won 56 percent of the points off Peng\'s serve. Ivanovic defeated No. 4-seeded Roberta Vinci 6-3, 6-3 in just 71 minutes. Ivanovic also won more than half the points when receiving serve and piled up five breaks in Vinci\'s nine service games. Ivanovic and Petrova will meet in Saturday\'s tournament semifinals. Ivanovic has a 6-5 series edge over Petrova. They have split their two previous meetings in 2011. Friday\'s schedule calls for top-seeded Marion Bartoli to go against Anabel Medina Garrigues while No. 3-seeded Sabine Lisicki takes on Daniela Hantuchova. The winners of those matches will also play in the semifinals The WTA\'s Tournament of Champions is the final event on the association\'s 2011 calendar.