Top seed Maria Sharapova made another poor start before storming back to beat home favourite Ai Sugiyama at the Pan Pacific Open in Tokyo on Friday.
Sharapova is going for her 16th career title in Tokyo
Sharapova had struggled past Francesca Schiavone in the previous round and again needed three sets.
But the Russian dominated sets two and three to beat Sugiyama 4-6 6-0 6-1 and set up a semi-final with Ana Ivanovic, who beat Jelena Jankovic 3-6 6-4 6-2.
Martina Hingis thrashed Samantha Stosur 6-0 6-1 and now plays Elena Dementieva.
Third seed Dementieva eased past Italian qualifier Roberta Vinci 6-1 6-2 in the last of the quarter-finals.
There are going to be days when your serve isn't working
Hingis won just two games against the Russian in the 2006 final and said: "If I play the way I did today I don't have to be afraid of anybody. I'll definitely want revenge."
"It's never easy against Sugiyama," said Sharapova.
"She had the crowd behind her and was able to take the first set, but I'm glad I was able to come back and win."
606 DEBATE: Your reaction to Sharapova's victory
With on-court coaching allowed in Tokyo, Sharapova had needed a stern talking to from Michael Joyce during her win over Schiavone, and it was the same against Sugiyama.
"She was playing aggressively in the first set and I wasn't making my shots," said Sharapova.
"Michael told me to move it around and play more aggressively, and I started making my shots and gave her less time to do what she wanted to do.
She added: "I worried about the serve a little too much in the first set.
"There are going to be days when your serve isn't working and when that happens you just have to concentrate on the things that are going well."