BIEL, Switzerland (AP) -- Top-seeded Barbora Strykova saved two set points to beat Carina Witthoeft of Germany 6-2, 7-6 (6) in the Biel Ladies Open second round on Thursday.
The 18th-ranked Czech let slip a 5-3 lead in the second set, then twice faced set point against the 69th-ranked Witthoeft before forcing the tiebreaker.
Strykova's 17-year-old compatriot, Marketa Vondrousova, also advanced to a first career quarterfinal at a tournament debuting on the WTA Tour.
Vondrousova, a left-hander ranked No. 233, eased past 60th-ranked Annika Beck of Germany 6-1, 6-3.
Second-seeded Carla Suarez Navarro of Spain exited, losing to Camila Giorgi of Italy 6-2, 6-7 (5), 6-2.
In Friday's quarterfinals, Strykova will play seventh-seeded Julia Goerges as the only seeds remaining in the draw.