Britain's Naomi Broady is through to the second round of the Abierto GNP Seguros WTA tournament in Monterrey after a straight-sets victory over young American Catherine Bellis.
Broady had to dig deep for a 7-6 (9/7) 6-4 success against the Californian teenager ranked 69 places above her at 54 in the world.
A hard-fought first set lasted more than 53 minutes in which both players were broken once, but big-serving Broady's 11 aces were decisive as she edged in front via a tie-break.
The 27-year-old from Stockport then broke again to go 2-1 up in the second set, and never relinquished the advantage – finishing with 17 aces to her opponent's one.
Broady will play either Hungary's Timea Babos or a qualifier in round two.
Meanwhile, second seed Anastasia Pavlyuchenkova eased past Tajana Maria 6-1 6-3 to advance to the second round, while third seed Caroline Garcia is also though after she rallied for a 4-6 6-2 6-3 win over wildcard Renata Zarazua.
Julia Boserup beat Nao Hibina 6-0 6-2 while Donna Vekic saw off Patricia Maria Tig 6-4 6-1.
At the Volvo Car Open in Charleston, Laura Siegemund beat Lesia Tsurenko 6-7 (6/8) 6-2 7-6 (6/4) to set up a second-round meeting with third seed Venus Williams.
Andrea Petkovic will face eighth seed Anastasija Sevastova after beating Lara Arruabarrena 7-5 6-2, while Jelena Jankovic will take on sixth seed Samatha Stosur following a 6-0 6-4 win over Ekaterina Alexandrova.
Alison Riske was given a work out by wildcard Kayla Day before advancing 7-5 4-6 6-0, while Monica Puig was 4-6 6-2 4-1 up when Katerina Siniakova, seeded 16th, withdrew with an injury.
There were also wins for Ons Jabeur, Jelena Ostapenko Naomi Osaka and Kateryna Bondarenko.
Play was called off for the day due to rain later in the evening, leaving a number of matches to be made up on Tuesday.
