Angelique Kerber fended off a determined Alla Kudryavtseva to complete the quarter-final line-up at the Monterrey Open.
German left-hander Kerber, who reached Wimbledon's semi-finals last year, took the opening set against her Russian opponent but was reeled in and taken to a decider.
When it mattered, she produced a performance befitting of her status at the tournament to seal a 6-4 4-6 6-2 victory and clinch a last-eight clash with Japanese eighth seed Ayumi Morita.
They finished late in the evening, long after Lauren Davis won her all-American second-round clash with Coco Vandeweghe 6-4 7-6 (10/8) and Russian third seed Maria Kirilenko saw off Serbian Jovana Jaksic 6-0 4-6 6-1.
Hungary's Timea Babos is the defending champion, and knocked out fourth seed Ana Ivanovic on Wednesday to reach the quarter-finals.