Johanna Konta booked her spot in the Abierto Monterrey Afirme quarter-finals as Caroline Wozniacki cruised on Wednesday.
Konta, the British fourth seed, overcame 13 double faults to edge past Belgian Yanina Wickmayer 7-6 (8-6) 7-6 (7-4) in Mexico.
Wickmayer was up a break in each set but failed to capitalise before Konta held her nerve in the tie-breaks on the hard courts at the WTA International event.
Awaiting Konta in the last eight is Kirsten Flipkens, who beat fellow Belgian Alison Van Uytvanck 6-2 4-6 6-3.
The only other second-round match on Wednesday saw Heather Watson ease past Polona Hercog 6-2 6-3.
Top seeds Sara Errani and Caroline Wozniacki had contrasting wins to start their tournaments.
Wozniacki, the Danish second seed, needed just 68 minutes to thrash Olga Govortsova 6-1 6-2.
Italy's Errani incredibly missed just four first serves in her 6-1 3-6 6-4 triumph over Magdalena Rybarikova.
A runner-up last year, French fifth seed Caroline Garcia was too good for qualifier Petra Martic in a 6-3 6-4 win.
Slovakian Dominika Cibulkova was downed by Estonian Anett Kontaveit 6-4 6-4 in the first round.