Danielle Collins needed seven match points to defeat Jil Teichmann at the Adelaide International 2 but ultimately progressed to the quarters.
Collins, seeded 10th, had victory in her grasp after reeling off four straight games in the second set.
Yet she was unable to get over the line at the first six times of asking, initially failing to serve out the win before Teichmann saved five match points.
Collins, though, regained momentum in the tie-break to win 6-3 7-6 (7-2).
World number nine Veronika Kudermetova is next up for Collins, having received a walkover to the last eight.
Caroline Garcia, the highest-ranked player left in the tournament, overcame Katerina Siniakova 6-3 3-6 7-5, but was made to work for her win.
Having been pegged back in the second set, Garcia seemed well set to push for victory when she went 3-1 up in the decider, but Siniakova broke and then held her serve to restore parity.
A tie-break looked likely until Garcia converted the third break point of a thrilling 12th game to claim victory.
Barbora Krejcikova, the 2021 French Open champion, was ousted by fifth seed Daria Kasatkina, who cruised through 6-2 7-5.
World number eight Kasatkina will take on two-time Wimbledon champion Petra Kvitova for a place in the last four.
Belinda Bencic also progressed, as did Paula Badosa and Beatriz Haddad Maia.
Anna Blinkova caused an upset at the Hobart International, dispatching top seed Marie Bouzkova 7-5 6-4.
Fifth seed Anhelina Kalinina is the favourite after Bouzkova's exit and a tie with 2019 champion Sofia Kenin is her reward for a win over Tatjana Maria.