Top-ranked Victoria Azarenka reached the quarterfinals of the Generali Ladies by beating Simona Halep of Romania 6-1, 6-1 on Thursday.
Azarenka dominated play from the baseline and had 20 winners.
Azarenka, who has lost four games in two matches, will next play either Petra Martic of Croatia or Patricia Mayr-Achleitner of Austria.
Bethanie Mattek-Sands reached her first quarterfinal of the season by defeating Carla Suarez Navarro of Spain 6-3, 6-3.
The 201st-ranked American, who is battling her way back up the rankings after recent hip, back and left foot injuries, will face Irina-Camelia Begu of Romania.
Begu, who lost in qualifying but replaced Anna Tatishvili of Georgia in the main draw, beat Kiki Bertens of the Netherlands 6-4, 7-6 (7).