Nadia Petrova of Russia shows her trophy after the final match against Caroline Wozniacki of Denmark at the WTA Tournament of the Champions in Sofia, Bulgaria, Nov. 4, 2012. Petrova won 2-0 to claim the title. (Xinhua/Chen Hang)

Nadia Petrova of Russia kisses her trophy after the final match against Caroline Wozniacki of Denmark at the WTA Tournament of the Champions in Sofia, Bulgaria, Nov. 4, 2012. Petrova won 2-0 to claim the title. (Xinhua/Chen Hang)

Caroline Wozniacki of Denmark competes during the final match against Nadia Petrova of Russia at the WTA Tournament of the Champions in Sofia, Bulgaria, Nov. 4, 2012. Petrova won 2-0 to claim the title. (Xinhua/Chen Hang)

Nadia Petrova of Russia (L) and Caroline Wozniacki of Denmark show their trophies after the final match against Nadia Petrova of Russia at the WTA Tournament of the Champions in Sofia, Bulgaria, Nov. 4, 2012. Petrova won 2-0 to claim the title. (Xinhua/Liu Zai)

Nadia Petrova of Russia competes during the final match against Caroline Wozniacki of Denmark at the WTA Tournament of the Champions in Sofia, Bulgaria, Nov. 4, 2012. Petrova won 2-0 to claim the title. (Xinhua/Chen Hang)

Nadia Petrova of Russia celebrates during the final match against Caroline Wozniacki of Denmark at the WTA Tournament of the Champions in Sofia, Bulgaria, Nov. 4, 2012. Petrova won 2-0 to claim the title. (Xinhua/Liu Zai)