Caroline Wozniacki wins opener
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The top-seeded Wozniacki defeated Hsieh Su-Wei of Taiwan 6-2, 6-2 in 60 minutes while it took Vinci five minutes longer to rout Slovakia's Daniela Hantuchova 6-1, 6-2.
Wozniacki converted all five of her break points and only lost her serve once, in the second set.
"I always try to finish my matches in two sets and I am happy that this time it worked," said Wozniacki, who is coming off titles in Seoul and Moscow. "I will try to finish this season with a hat trick."
The fourth-seeded Vinci dominated throughout, breaking five times. The two traded breaks to start the second set, but the Italian then jumped out to a 4-1 lead to take control.
Wozniacki will play Vinci on Wednesday, with the winner likely clinching a spot in Saturday's semifinals. The first two in each group advance.
In the other group, Bulgaria's Tsvetana Pironkova came from behind to dispatch sixth-seeded Zheng Jie of China 2-6, 6-4, 7-6 (4). Pironkova took a 3-0 lead in the third set before being forced into a tiebreaker.
The Tournament of Champions features the six highest-ranked players who have won a title during the season but did not qualify for the WTA Championships, along with two wild cards.
It is the final event on the WTA calendar.
Copyright 2012 by The Associated Press
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