Vera Zvonareva and Sam Stosur kept the year-end No. 1 ranking in play in Doha, with No. 2 Zvonareva going to 2-0 in round-robin play and Samantha Stosur beating No. 1 Caroline Wozniacki.
To reach No. 1, Zvonareva must win the title without losing a match and have Wozniacki not win another match in the competition.
Stosur, also up 2-0 in round robin play, can clinch her passage to the semifinals when she plays Elena Dementieva on Thursday.
The current standings are:
Maroon Group win-loss (sets won-lost)
Samantha Stosur 2-0 (4-0)
Caroline Wozniacki 1-1 (2-2)
Francesca Schiavone 0-1 (0-2)
Elena Dementieva 0-1 0-2
White Group win-loss (sets won-lost)
Vera Zvonareva 2-0 (4-0)
Kim Clijsters 1-0 (2-0)
Victoria Azarenka 0-1 (0-2)
Jelena Jankovic 0-2 (0-4)