Ivanovic wins again at TOC

Sofia, Bulgaria ( - Two-time champion Ana Ivanovic posted another round-robin victory Thursday at the season-ending WTA Tournament of Champions.

The second-seeded, former world No. 1 and former French Open champ held off fourth-seeded former U.S. Open titlist Samantha Stosur 6-2, 5-7, 6-2 on the indoor hardcourt at Armeets Arena. Ivanovic captured this event back-to-back in 2010 and 2011 in Bali.

This tournament features an eight-woman field that is divided into two groups. Round-robin play will be staged through Friday, with the semifinals on Saturday and a Sunday final.

Group Sredets is comprised of the 2-0 Ivanovic, Stosur (1-1), fifth seed Elena Vesnina (1-1) and eighth-seeded Tsvetana Pironkova (0-2). Vesnina topped Pironkova 6-2, 4-6, 6-0 on Day 3.

Group Serdika features top seed Simona Halep (2-0), third-seeded Russian Maria Kirilenko (0-1), sixth-seeded Russian Anastasia Pavlyuchenkova (1-1) and seventh-seeded Frenchwoman Alize Cornet (1-1). An injured Kirilenko was replaced in the field this week by alternate Elina Svitolina (0-1).

The field consists of the six highest-ranked players who won at least one International Series tournament during the year and did not qualify for last week's WTA Championships in Istanbul or are not participating in this week's Fed Cup final. Ivanovic and Pironkova were invited as wild cards.