It's down to four. Maria Sharapova and Svetlana Kuznetsova will play one semifinal, and Jelena Jankovic and Ana Ivanovic will play the other. Sharapova and Kuznetsova have played each other seven times, and Sharapova has won four of those matches, including the last two. Sharapova leads 3-2 on hard courts.
Jankovic and Ivanovic have played each other six times, and Ivanovic has won five of those matches. She leads 3-1 on hard courts.
Possible interfering factors:
Ivanovic appeared to be bothered by the heat in her quarterfinal match against Vera Zvonareva. I say "appeared" because I'm not totally convinced she wasn't more bothered by Zvonareva's backhand. At 4-all int he second set, Ivanovic insisted (the umpire suggested she wait until the changeover) on taking a time-out to see the trainer, who felt her pulse while she had a drink and a bite to eat. She then returned to the court and broke Zvonareva.
Jankovic has been suffering with a cold since she arrived in Indian Wells. Having Wednesday off and having her quarterfinal opponent retire certainly helps, but illness lurks.