Top-seed Kiki Bertens stormed past Russia's Veronika Kudermetova, while third-seed Petra Kvitova edged Belgium's Alison Van Uytvanck, to reach the quarterfinals of the St. Petersburg Ladies Trophy in Russia on Thursday.
Bertens defeated Kudermetova inside of 57 minutes, serving six aces in a 6-1, 6-2 straight sets victory.
Kvitova won a closely contested opening set, ending when the Czech raced through a tiebreaker, before Van Uytvanck hit back in the second, breaking Kvitova's serve three times.
World No. 11 Kvitova was knocked out in the quarterfinals of last month's Australian Open against Ashleigh Barty.