After seeing off former world number one Jelena Jankovic at the Ladies Championship Gstaad, Rebeka Masarova moved into the last eight with a win over Anett Kontaveit.
The 16-year-old world number 797 celebrated her WTA Tour debut with victory over Jankovic, and the fairytale continued on Friday thanks to a three-set win.
Makarova prevailed 7-6 (7-2) 4-6 6-2 to set up a quarter-final clash with Annika Beck, who was one of two women to play and win twice in the same day.
Due to heavy rain in Switzerland earlier in the week, some first-round matches were yet to get under way until Friday.
Fifth seed Beck came from a set down to beat Marina Erakovic 3-6 6-2 7-5, but she showed no signs of fatigue in her second match of the day as she eased beyond Katerina Siniakova 6-2 6-1.
The other woman to enjoy double success was Kiki Bertens, who saw off Tamira Paszek 5-7 6-2 6-4 and then Claire Feuerstein 7-6 (11-9) 6-1.
Berterns will meet Irina Khromacheva in the quarters after the latter's 7-5 6-3 win over Julia Goerges, while Carina Witthoeft will face Viktorija Golubic following their wins on Friday.
Meanwhile, Johanna Larsson defeated Amra Sadikovic 6-3 6-4 to book a quarter-final against top seed Timea Bacsinszky, who had little trouble in her 6-2 6-2 win over Mandy Minella.