Stosur beats Wozniacki, gives Vera a shot at top spot.

Her big serve and laser-like forehand in full flight, Samantha Stosur pulled off the first big upset of the season-ending WTA Championships - Doha 2010, dispatching Caroline Wozniacki, the world No.1, 6-4 6-3.

Stosur, the No.5 seed in Doha, gave Wozniacki some windows on her serve, six break points to be exact - but she saved them all and snuck out two breaks of her own against the top seed, one in the last game of the first set and another to go up 3-1 in the second. She hit a service winner on match point.

"Anytime you beat the No.1 player in the world it's a good thing," said Stosur, who hit 26 winners in the match. "It's so exciting to be here. Everything seems to be coming together. Hopefully I can keep playing like this."

Stosur scored her second career victory over a reigning No.1, her first coming earlier this year at the French Open, where she beat Serena Williams in a nail-biter in the quarters. Stosur is the only Australian in the last seven years to beat a No.1 (before her, the last one to do it was Jelena Dokic in 2003).

Stosur is now 2-0 in her group, having beaten No.4 seed Francesca Schiavone Tuesday; Wozniacki is now 1-1, having beaten No.7 seed Elena Dementieva.

In other matches on Day 2 of round robin play in Doha, No.2 seed Vera Zvonareva edged No.8 seed Victoria Azarenka, 7-6(4) 6-4, while No.3 seed Kim Clijsters beat No.6 seed Jelena Jankovic, 6-2 6-3.

Zvonareva was trailing 4-2 in the first set and 3-1 in the second set before toughing out her win over Azarenka. "I'm always leaving 100% on the court when I'm out there. I'm happy I was able to come back in those two sets; I shouldn't have started that slowly, but I was just trying to find my rhythm. I made the right adjustments and came up with great tennis in the tie-break when I needed it."

Clijsters had 10 double faults in her match but still found a way to win handily. "It wasn't my best tennis, but it was good enough. I felt I did a lot of good things, and there are a few things I need to tweak. The more matches I get, the better."