(CNN) -- Samantha Stosur stopped Caroline Wozniacki from clinching the year-end women's No. 1 tennis ranking with a shock 6-4 6-3 victory at the WTA Championships in Qatar on Wednesday night. 

The Australian romped to her second straight victory in the Maroon Group, following her revenge win over French Open champion Francesca Schiavone on Tuesday. 

The Roland Garros runner-up's kick serve was a potent weapon against Wozniacki, with the triumph giving the 26-year-old every chance of reaching the semifinals ahead of her final group match against Russia's Elena Dementieva on Thursday. 

It was her second victory over a top-ranked player this year, having beaten Serena Williams on the way to reaching the final in Paris. 

The fifth seed fired 26 winners to Wozniacki's 14, and could afford to serve two double-faults in the deciding game before the Dane returned a backhand long on her first match-point. 

Wozniacki, who thrashed seventh seed Dementieva on Tuesday, will next take on Italy's Schiavone on Thursday. 

Kim Clijsters, who won the $4.5 million season-ending event in 2002 and 2003, earlier triumphed in her opening White Group match 6-2 6-3 against fellow former No. 1 Jelena Jankovic despite serving 10 double-faults. 

The Belgian, returning to action after having a mole cut off her foot, broke Jankovic to love in the first game of the match and then again in the seventh. 

The three-time U.S. Open champion was less impressive in the second set but had enough to see off the Serbian, who is struggling with illness in the oppressive heat in Doha. 
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who won the $4.5 million season-ending event in 2002