Reigning champ Ivanovic, Petrova reach semis in Bali

Last year's winner Ana Ivanovic and former 10 star Nadia Petrova posted upset victories on Thursday to reach the ending Commonwealth Bank Tournament of Champions tennis event.

The former world No. 1 Ivanovic erased fourth-seeded Italian Roberta Vinci 6-3, 6-3 in 70 minutes, while the Russian Petrova handled second-seeded Chinese Peng Shuai 6-4, 6-3 in just under an hour-and-a-half on Day 1.

Four opening-round matches here will produce four semifinalists at this eight- player, four-day event on the hardcourts at Westin Resort Nusa Dua. The wild card Ivanovic will face Petrova in one of the semis on Saturday. The Serbian Ivanovic is 6-5 lifetime against Petrova, including a 1-1 mark this season.

The former French Open champion Ivanovic topped Russian Alisa Kleybanova in last year's finale in Bali.

Friday's matches will pit top-seeded French slugger Marion Bartoli against Spaniard Anabel Medina Garrigues and third-seeded German Sabine Lisicki versus former top-10 performer Daniela Hantuchova of Slovakia.

The winner of this $600,000 third-year tournament will collect $210,000. It features the six highest-ranked players who have won a title during the year but failed to qualify for the WTA Championships and two wild cards.

This is the final WTA event of 2011.