Osaka (Japan): World No.134 Chang Kai-Chen stunned top seed Sam Stosur of Australia in the semifinal of the Japan Open here Saturday.
Taiwan`s Chang overcame six double faults and hit four aces to beat the world No. 9 6-4, 4-6, 7-6(3) in their first-ever encounter.
Stosur won the Osaka title in 2009 and was last year`s runner-up, losing to France`s Marion Bartoli. She hasn`t won any titles since winning the US Open last year.
Chang will play Britain`s Heather Watson in the final after Watson overpowered local player Misaki Doi 7-6(2), 7-5 in their semi-final earlier Saturday.
It is a maiden career singles final for both Chang and Watson.
The prize fund for the tournament is USD 220,000.