Magdalena Rybarikova and Barbora Strycova both safely moved into the Linz Open quarter-finals with victories on Thursday.
Rybarikova was pushed hard by Carina Witthoeft but came through her clash with the German 7-6 (7-4) 6-3 after battling to win a tie-break following a first set that saw only one break point.
Witthoeft immediately broke to take control of the second, but Rybarikova subsequently recovered from 3-2 down to take four successive games and wrap up a hard-fought match.
Strycova dropped the opening set against Croatian 20-year-old Jana Fett after losing her serve three times, but came back to win 2-6 6-3 6-3 in the first match of the day.
Top seed Rybarikova will play Sorana Cirstea next after the Romanian eventually prevailed over Natalia Vikhlyantseva thanks to a marathon first set tie-break, winning 7-6 (16-14) 6-4 in just over two hours.
Viktoriya Tomova looked on track for a big win against Viktorija Golubic, but the Swiss player bounced back after a slow start to triumph 4-6 6-4 6-1 and Golubic's reward will be a quarter-final meeting on Friday with Johanna Larsson, who comfortably beat Varvara Lepchenko 6-2 6-3.