Defending champion Serena Williams beat Kaia Kanepi of Estonia 6-3 6-3 yesterday to set up a repeat of last year's Sony Ericsson Open final against world number one Justine Henin in the last eight.
Henin, seeking her first title of 2008, wasted little energy in a 6-2 6-2 fourth-round win over world number 53 Elena Vesnina of Russia.
Williams's sister Venus lined up a quarter-final against world number four Svetlana Kuznetsova after beating Danish teenager Caroline Wozniacki 6-3 6-3.
Third-seeded Kuznetsova sealed a 7-6 6-3 victory over 16th-seeded Shahar Peer of Israel, avenging her defeat by the same player in Miami last year.
Men's world number one Roger Federer had a short day at the office when his opponent Robin Soderling of Sweden retired from their third-round match trailing 6-4 3-0 because of illness.
Federer served well but did allow world number 39 Soderling to break him in the fifth game of the first set.
"It's a big difference between not playing at all or playing one and a half sets," Federer told reporters. "My opponent was a dangerous player. I think it was good for me to go out there and play today."