Veteran Venus Williams fought her way into the Bank of the West Classic quarter-finals as Caroline Wozniacki succumbed to injury in Washington.
A two-time champion in Stanford, Williams overcame Magda Linette 6-3 6-7 (6-8) 6-2 at the WTA Premier event on Wednesday.
Williams needed two hours, 14 minutes to earn her second-round win.
Johanna Konta and Misaki Doi also advanced, while seventh seed Alize Cornet was beaten.
Konta thrashed Julia Boserup 6-3 6-1 and Doi won an all-Japanese affair against Nao Hibino 6-3 6-4.
But Cornet was no match for Zheng Saisai, suffering a 6-4 6-1 loss.
In Washington, Wozniacki led Samantha Stosur 7-5 3-4 when the Dane retired due to an elbow injury.
In other second-round matches, Yanina Wickmayer claimed a 6-3 7-5 win over Zhang Shuai and wildcard Jessica Pegula beat Christina McHale 7-5 6-2.
Kristina Mladenovic completed her opener against Samantha Crawford, winning 6-2 2-6 6-3.
Lauren Davis was pushed far more before registering a 5-7 7-5 6-3 victory over Shelby Rogers, while Yulia Putintseva edged past American teenager Usue Maitane Arconada 6-4 4-6 6-4.