Yanina Wickmayer overcame a slow start against Julia Boserup as she booked her spot in the second round at the Carlsbad Classic.
Top-seeded Belgian Wickmayer won a first-set tie-break in Tuesday's 7-6 (7-3) 6-3 victory in California.
The 2009 US Open semi-finalist broke serve on five occasions and saved seven break points against the American in an hour, 32 minutes on court at the WTA 125k Series tournament.
Next up for Wickmayer is Kristie Ahn, who saw off Dalila Jakupovic 6-4 4-6 6-4.
German second seed Tatjana Maria also progressed to the second round courtesy of a straight-sets win over Nicole Mossmer.
Maria triumphed 6-1 6-4 to setup a showdown with Canadian qualifier Francoise Abanda.
Abanda blitzed Zoe Gwen Scandalis 6-1 6-1.
There was no such luck for fellow seeds Julia Glushko (sixth) and Sachia Vickery (seventh).
Israeli Glushko came unstuck at the hands of Catherine Bellis, who won 6-3 6-4.
American Vickery lost out to Elitsa Kostova 6-4 6-2.
Elsewhere, Maria Sakkari crushed Brett Berger 6-0 6-0, while Veronica Cepede Royg accounted for Gabriela Ce 6-0 6-3.