ISTANBUL (AP) Top-ranked Caroline Wozniacki rallied past Agnieszka Radwanska 5-7, 6-2, 6-4 Tuesday in their opening round-robin match at the WTA Championships.

Wozniacki wasted a 4-2 lead in the third set but broke again when Radwanska netted a forehand on the Dane's second match point.

Radwanska converted both her break points to take the first set. The second set featured six breaks of serve, with Wozniacki getting four.

In the early Red Group match, Wimbledon champion Petra Kvitova defeated Vera Zvonareva of Russia 6-2, 6-4.

Making her first appearance at the season-ending tournament for the top eight players , Kvitova let a 4-1 lead slip to 4-all in the second set but broke again before wrapping up the win.

Later, Maria Sharapova will play U.S. Open champion Sam Stosur in the White Group.