Danielle Collins eased past Shelby Rogers 6-4 6-3 to book her spot in the second round at the Silicon Valley Classic on Tuesday.
World number 36 Collins proved too strong for American compatriot Rogers, winning in one hour and 25 minutes.
Collins will meet another American in the second round, with Sloane Stephens up next.
Former U.S. Open winner Stephens beat Caty McNally 6-4 6-2 earlier in the day.
Yulia Putintseva, meanwhile, eased her way into the second round with a 7-5 6-3 win over Croatian Donna Vekic.
Putintseva will face Australian Ajla Tomljanovic in the second round after she fought back to overcome Amanda Anisimova 1-6 7-5 7-5.
France's Kristina Mladenovic won 6-4 6-4 over Han Na-Lae, while American Claire Liu won in three sets against Dayana Yastremska.
Mladenovic will face top seed Elise Mertens, while Liu meets second seed Elena Rybakina.