PONTE VEDRA BEACH, Fla. — Canadian Aleksandra Wozniak upset top-seeded Nadia Petrova 6-4, 4-6, 6-2 today in the semifinals of The MPS Group Championships.

She will meet second-seeded Caroline Wozniacki, who beat Elena Vesnina in the other semifinal 2-6, 6-3, 7-6 (4).

Wozniak, the tournament's No. 5 seed, won the first set and led 4-1 in the second before Petrova, ranked 10th in the world, came back to win five straight games.

"She stepped it up in the second set," Wozniak said. "I started backing up. Of course, my emotions got involved, but I found my composure in the third set. It feels good to beat the top seed and a top-10 player."

Wozniak, who had 35 winners, built a 3-0 lead in the third set. She withstood the Russian's rally with a variety of well-placed shots to every area of the court.

"She played really well," Petrova said. "I've never seen anybody paint more lines than she did today."

Petrova, coming back from a stress reaction injury to her right foot, said she's not disappointed with the loss.

"Two weeks ago they were talking about surgery so I am lucky to be able to play," she said. "I know when I get my feet back I'll play good tennis."

The winner will receive $37,000 of the $220,000 purse.

The top-seeded doubles team of Lisa Raymond and Kveta Peschke beat Wozniacki and Barbora Zahlavova Strycova 4-6, 7-5, 15-13. They will play unseeded Chia-Jung Chuang of Taiwan and Sania Mirza in the final. Chuang and Mirza beat American Angela Haynes and Liga Dekmeijere 6-4, 7-5.