Andrea Petkovic dug deep to recover from a set down to beat German compatriot Carina Witthoeft at the Bank Of The West Classic.
World number 54 Witthoeft flew out of the blocks, taking a 5-1 lead in the first set, before Petkovic got back into it only to still lose the opener 7-5.
From there sixth seed Petkovic showed her class, near-sweeping the board on the way to a 6-1 second-set triumph in just 24 minutes and then edging the decider 6-3.
Another German, Mona Barthel, now awaits for Petkovic in the second round after the world number 63 made light work of Canadian wildcard Carol Zhao 6-3 6-0.
Seventh seed Madison Keys had a similarly comfortable day's work, cruising past Aleksandra Krunic 6-3 6-0.
Elsewhere there were wins for Alison Riske, Misaki Doi and Nicole Gibbs.
Source: PA
