Serena Williams eased back into action with a 6-2 6-1 win over American wildcard Nicole Gibbs in the second round of the Bank of the West Classic.
Having received a bye in the first round, this was Williams' first match since winning her fifth Wimbledon singles title on Saturday.
The top seed wasted little time, dispatching American college champion Gibbs, 19, in an hour and two minutes.
The home fans at Stanford University, where Gibbs is a sophomore, had little to cheer about, but world number 403 Gibbs, who was a ball girl for the Wimbledon champion when she was 12, did break the Williams serve in the second set.
Williams will next face sixth seed Chanelle Scheepers of South Africa, who beat Portugal's Michelle Larcher de Brito 6-3 6-4.
American lucky loser Coco Vandeweghe created an upset as she defeated former world number one and fourth seed Jelena Jankovic 6-4 6-2.
Fifth seed Yanina Wickmayer recovered from losing the first set to beat Britain's Heather Watson 5-7 6-1 6-4.