World No. 1 Victoria Azarenka saved two match points in her opening-match victory, while two-time titlist Serena Williams improved to 2-0 in round-robin play at the season-ending WTA Championships in Istanbul.
Azarenka staved off fifth-seeded German left-hander Angelique Kerber 6-7 (11-13), 7-6 (7-2), 6-4 in a high-quality 3-hour, 6-minute battle on Wednesday. The Belarusian star saved the match points en route to forcing a second-set tiebreak, which she wound up dominating before coming out on top in a tight third.
The 23-year-old Azarenka now needs only one more win this week to end the year at No. 1.
Azarenka and Williams will square off on Thursday, with the American seeking a fifth win in five tries this year. Williams beat Azarenka in last month's U.S. Open finale.
The Australian Open champion Azarenka was last year's WTA Championships runner-up to Czech southpaw Petra Kvitova, who pulled out of the Istanbul field on Wednesday due to a viral illness.
Meanwhile, the third-seeded former top-ranked great Williams got past eighth- seeded former French Open champion Li Na, 7-6 (7-2), 6-3, indoors at Sinan Erdem Dome. The powerful American smacked six aces in the 1-hour, 50-minute victory.
The 2012 Wimbledon, U.S. Open and Olympic champion Williams captured WTA Championships titles in 2001 and 2009 and is a two-time runner-up at this prestigious event.
This week's four-player Group A features Azarenka (1-0), Williams (2-0), Kerber (0-2) and Li (0-1), while Group B boasts second-seeded 2004 champion and 2007 WTA Championships runner-up Maria Sharapova (1-0), Wimbledon runner- up Agnieszka Radwanska (1-0), seventh-seeded French Open runner-up Sara Errani (0-1) and Sam Stosur, who replaced last year's Championships winner Kvitova in this week's field.
The top-two players in each group will advance to the semifinals. with the winners squaring off in the lucrative final on Sunday.
Also in Istanbul on Thursday, Kerber will face Li and Errani will tangle with a ninth-seeded Stosur.
The winner of this $4.9 million event could collect as much as $1.75 million.