Petrova upsets Stosur

Tokyo - Russia's Nadia Petrova overpowered eighth seed Samantha Stosur 6-4 6-2 in a surprisingly one-sided match to reach the final of the Pan Pacific Open on Friday.

Petrova, struggling with lower back pain all week, ran Australian Stosur ragged along the baseline to advance to her first final at the WTA premier five event in Tokyo.

The 17th seed faces the winner of the day's second semi-final between defending champion Agnieszka Radwanska and German Angelique Kerber in Saturday's championship match.

Petrova, chasing her second title of the season, came into the match with a 5-3 record over Stosur, last year's US Open champion.

Stosur committed a string of unforced errors and Petrova closed out the match following another wild forehand from the Australian after one hour, 47 minutes.

Nine of the world's top 10 women made the trip to Tokyo, although the $2.16 million hard-court tournament lost its two top seeds, Victoria Azarenka and Maria Sharapova, on Thursday.