China's Li Na returns to Russia's Maria Sharapova at the?WTA Championship finals in Istanbul, Turkey on?Wednesday, Oct. 26, 2011.

Li Na got right back on the winning track and Maria Sharapova's quest for the year-end No.1 ranking took another hit Wednesday, as the Chinese beat the Russian in straight sets 7-6 (4), 6-4 at WTA Championships.

Li had been struggling since becoming Asia's first Grand Slam champion at the French Open, going 5-7 in her seven tournaments since - but she had won her last three meetings against Sharapova in straight sets and brought that magic out again.

Sharapova led 4-1 in the opening set and after seeing her lead evaporate she then moved 4-0 ahead in the tiebreak only to lose the next seven points with a run of unforced errors.

Li, who beat Sharapova in the French Open semi-finals this year, moved into a 5-2 lead in the second set before an attack of the jitters almost proved costly.

Serving for the match at 5-4 Li slipped 15-40 behind as Sharapova blazed away but she held her nerve to claim victory at the first attempt when her opponent hammered a backhand return over the baseline.

"I really wasn't thinking about too much during the match," Li said in her on-court interview. "I knew I had a chance to come back. The match is never finished until it's finished. I'm so happy I was able to beat Maria because she's a top player, and also today was my first match ever at the Championships, so I want to thank all the crowd here for supporting me."

Li is the first Chinese player to qualify for the season-ending event for the world's top eight players.

Russia's Maria Sharapova returns to China's Li Na at the WTA Championship finals in Istanbul, Turkey on Wednesday, Oct. 26, 2011.