Samantha Stosur prevailed in straight sets against Maria Sharapova to advance to the Pan Pacific Open semi-finals in Tokyo.
Stosur triumphed 6-4, 7-6 (12-10) to set up a clash with another Russian, Nadia Petrova, in the last four.
Petrova came from behind to beat Sara Errani of Italy 3-6, 7-5, 6-3.
Two-time champion Sharapova took a service break lead first in both sets, losing the advantage both times before coming back from 3-5 down in the second set to force a tie-breaker.
Sharapova staved off four match points in the tie-breaker, but surrendered the match on Stosur's fifth match point.
"It was tough, Stosur said.
"I knew I lost nine points in a row (at 5-3 in the second set). I just tried to start well in the tie-breaker and I did get off to a good start. I just tried to keep going forward.
"In the tie-breaker, I had match points and she had set points. You don't get a few in a row and you don't know what happens. I just tried to keep going forward."
Meanwhile, world number one Victoria Azarenka withdrew from the tournament because of fatigue.
ABC/AFPTags: tennis, sport, japan First posted September 27, 2012 20:38:56