Kicking off her Indian Wells campaign having been gifted a first-round bye, Caroline Wozniacki cruised to a 6-4 6-1 win.
It was far from a perfect performance but former world number one Serena Williams managed to outlast Kiki Bertens 7-6 (7-5) 7-5.
Magdalena Rybarikova saved 11 match points in one game at the Indian Wells Masters, but still suffered a shock loss to Sofya Zhuk.
Entertaining Frenchman Gael Monfils was too good for Matthew Ebden on Friday, winning in straight sets.
Garbine Muguruza appeared destined to cruise into the third round on Friday – leading 6-2 3-0 but the Spanish star was bundled out.
Maria Sharapova and Sven Groeneveld split on Friday, having teamed up in 2014, winning seven titles, including the 2014 French Open.
Kristyna Pliskova failed to take advantage of a sluggish start from Simona Halep as the world number one moved into the third round.
Serena Williams is returning to the WTA Tour this week, but Simona Halep would see it as a positive if she does not dominate.
Serena Williams, a 23-time grand slam champion, is relishing the opportunity to play without pressure as she makes her return to the court.
American great Serena Williams made her long-awaited return to the WTA Tour and proved too good for Zarina Diyas on Thursday.