Top seed Victoria Azarenka overcame a lapse of concentration to defeat Ana Ivanovic 6-0 4-6 6-3 and reach the final of the Carlsbad Open on Saturday.
Playing in her first tournament since injuring her knee and hip at Wimbledon, Azarenka dug herself out of a second set hole to subdue the 2008 French Open champion, who also ran hot and cold throughout.
Azarenka will face the winner of the semi-final between Australian fifth seed Samantha Stosur and wild card Virginie Razzano of France.
"It's something that you expect from Ana, she's a very big shot maker and loves to bang the ball," Azarenka told reporters of the hard-hitting Serb.
"For me the key was to not let her make those shots and be the one who was putting the pressure. I did feel more consistent."
World number three Azarenka raced through the first set, breaking the seventh-seeded Ivanovic three times, but was less than thrilled with her play in the second, where she was broken to love and conceded it with three sizzling forehand winners.
Azarenka composed herself in the third, breaking Ivanovic with a ripping forehand crosscourt winner and never giving the Serb a look at her serve.
Former world number one Ivanovic, who has not won a title in a year and a half, rued giving away too many easy points at the important moments.
"That's about belief against these kind of players. If you give her chances she's going to use them."
Two-times Australian Open champion Azarenka is guaranteed to pass Russian Maria Sharapova for the number two ranking when they are released on Monday. Serena Williams is ranked number one.
Azarenka has won 28 straight matches on outdoor hard courts dating back to the 2012 US Open final, but she withdrew from three tournaments during the period with injuries.
"The reality is we have most of the tournaments on hard, but that's a great statistic," Azarenka said.