Second seed Maria Sharapova crushed defending champion Mary Pierce 6-2, 6-3 to reach the Acura Classic semi-finals on Friday.
The Russian will meet fifth seed Patty Schnyder of Switzerland, who beat number four Elena Dementieva 6-4, 6-3.
Seventh seed Nicole Vaidisova of Czech Republic also advanced to the final four with a 3-6, 6-4, 6-3 win over Russian Anna Chakvetadze.
Playing only her third match in sixth months, the 31-year-old Pierce looked sluggish and looked to be struggling with injury.
"My legs have been getting more sore every day," said Pierce, who has been off much of the year with a foot problem.
Sharapova dictated with her big serve and powerful ground strokes, occasionally charging into the net.
"You don't know how you are going to play after a long break and I played three opponents with three different games and I've come out and feeling solid and healthy," said Sharapova, who has won only one title this year.
"I've been working on things, like coming in and seeing those opportunities. I've been stupid the last few times so I'm learning my lesson. No matter how good or bad I feel, I still need to go into net."
The left-handed Schnyder outwitted Dementieva with clever variations, pulling her Russian opponent wide and attacking her backhand.
"From the first set on, I really played my game," Schnyder said. "I felt the ball so nicely. You don't know what she will do because she can attack, spin, run well and today she served really well.
With her comeback win over Chakvetadze, Vaidisova assured herself of a place in the world's top 10 next week.
"It's great," Vaidisova said. "I didn't think it would come this soon, but I'm still going to try to go as far as possible."
Vaidisova will meet the winner of the late match between top seed Kim Clijsters and five-times Grand Slam champion Martina Hingis.