Caroline Wozniacki defeated Roberta Vinci of Italy 6-3, 6-1 Wednesday to advance to the semifinals of the Tournament of Champions.
It was the second win for the top-seeded Dane in the group-stage format after her victory over Hsieh Su-Wei of Taiwan the previous day.
"I played solid and served very well. I am pleased with my performance,'' Wozniacki said.
Russian duo Nadia Petrova and Maria Kirilenko earned straight-set victories in their first group matches.
The second-seeded Petrova defeated No. 6 Zheng Jie 6-3, 6-3, handing her Chinese opponent a second loss in two days which will likely leave her without a chance of reaching the semifinals.
In the other match in the group, the third-seeded Kirilenko beat Tsvetana Pironkova 6-1, 6-4. Pironkova broke for a 2-0 lead in the second set but Kirilenko then won the next four games to take firm control of the match.
Petrova and Kirilenko will meet on Thursday.