Top seeds Petra Kvitova and Roberta Vinci moved into the quarterfinals at the inaugural Katowice Open.
The world No. 8 former Wimbledon champion Kvitova handled Luxembourg's Mandy Minella 7-5, 6-2, while Vinci came from behind to beat Dutchwoman Kiki Bertens 2-6, 6-3, 6-4 on the indoor surface at Spodek.
The Czech Kvitova's quarterfinal opponent on Friday will be Croat Petra Martic, while the Italian Vinci will battle Czech wild card Karolina Pliskova.
In other second-round play on Day 4, Israeli lucky loser Shahar Peer whipped 38-year-old American qualifier Jill Craybas 6-1, 6-3 and qualifier Alexandra Cadantu overcame Romanian compatriot Irina-Camelia Begu 4-6, 6-3, 6-4.
Friday's other quarters will pit Peer against Cadantu and German Annika Beck versus Italian qualifier Maria Elena Camerin.
This week's winner will pocket $40,000.