Russia's two-time champion Maria Sharapova eased into the Italian Open quarter-finals by defeating Bojana Jovanovski 6-3 6-3 in Rome.
Czech Petra Kvitova beat Jelena Jankovic 6-3 6-2 while Romania's Simona Halep overcame Venus Williams 6-2 6-1.
Spain's Carla Suarez Navarro played for more than three hours to beat Eugenie Bouchard 6-7 (2-7) 7-5 7-6 (9-7).
World number one Serena Williams withdrew with an elbow injury shortly before facing Christina McHale.
In other matches, there were wins for two-time Australian Open champion Victoria Azarenka, Daria Gavrilova and Alexandra Dulgheru.