ISTANBUL — Maria Sharapova pulled out of the WTA Championships with a sore ankle Wednesday after losing her second straight match at the season-ending tournament.

ISTANBUL — Maria Sharapova pulled out of the WTA Championships with a sore ankle Wednesday after losing her second straight match at the season-ending tournament.

The second-ranked Russian's withdrawal ensures that Caroline Wozniacki will finish the year with the No. 1 ranking, despite losing her group-stage match against Russia's Vera Zvonareva.

Sharapova entered the tournament after sitting out since withdrawing in the quarterfinals in Tokyo last month because of an ankle injury.

After losing 7-6 (4), 6-4 to Li Na in her second round-robin match Wednesday, Sharapova said "the ankle didn't recover as well as I had hoped after the first round."

Sharapova lost to Sam Stosur in her opening match on Tuesday.

The Russian will be replaced by alternate Marion Bartoli, who will face Victoria Azarenka of Belarus in the final group round. Azarenka maintained her perfect record against Sam Stosur with a 6-2, 6-2 win earlier Wednesday.

Wozniacki fell to 1-1 in the round-robin phase after losing 6-2, 4-6, 6-3 against Zvonareva in the late match. Even with the loss, she will finish at No. 1 in the rankings for the second year in a row, despite never having won a major. Sharapova was the only player with a chance to overtake the Dane going into the tournament.

Sharapova led 4-2 in the first set before Li broke back to force the tiebreaker, where the Russian let a 4-0 lead slip away. Li then took a 5-2 lead in the second and served out the match on her second attempt.