ISTANBUL (AP) -- Li Na outlasted former doubles partner Jelena Jankovic 6-3, 2-6, 6-3 for her second victory in two matches at the WTA Championships on Thursday.
The key to the error-filled match full of long rallies was Li's break of serve in the third set for a 4-3 lead. She never looked behind again.
The fourth-seeded Li has a 2-0 record in her group and looks likely to advance to the semifinals for the first time. Seventh-seeded Jankovic is 1-1. Jankovic is back in the tournament for the first time in three years.
The tournament brings together the top eight players in the world, who are split into two round-robin groups. The two top finishers in each pool advance to the semifinals.
Li beat Jankovic in the round of 16 at the U.S. Open.