Sixth-seeded Andrea Petkovic beat Carina Witthöft, 5-7, 6-1, 6-3, in the first round of the Bank of the West Classic in Stanford, Calif.
CiCi Bellis lost her opening match of the tournament, the first for female players in the annual United States Open series, to the qualifier Misaki Doi, 6-3, 7-6 (3). Last year, Bellis was the youngest player in 15 years to win a match at the U.S. Open. Doi will meet the No. 2 seed, Agnieszka Radwanska, on Thursday.
Nicole Gibbs, a qualifier who won two N.C.A.A. singles titles while at Stanford, beat Caroline Garcia, 6-4, 7-5, for her first WTA main-draw victory since April.