Defending champion Maria Sharapova continued her return to form as she swept past Colombia's Mariana Duque-Marino at the Madrid Open.
Sharapova, 28, had lost early in her last three tournaments but beat Duque-Marino 6-1 6-2 to reach the last 16.
Czech fourth seed Petra Kvitova came through a testing encounter against American Coco Vandeweghe 6-4 2-6 6-3.
Victoria Azarenka beat Ajla Tomljanovic 6-3 6-3 to set up a third-round meeting with American top seed Serena Williams.
Third seed Sharapova broke Duque-Marino's serve four times while saving three break points on her own serve.
The Russian will replace Simona Halep as world number two if she reaches the final, after the Romanian lost her opening match.
"I face the ranking questions every single week obviously because ranking is a big part of the sport," said Sharapova.
"It's not my main purpose and my main goal. If I'm not ready to beat someone towards the later stage of a tournament, then I'm not ready to beat them from the very beginning.
"My goal is to win championships."
In the men's event, Canada's fifth seed Milos Raonic beat Juan Monaco 6-3 6-4, 13th seed Gael Monfils thrashed Serb Viktor Troicki 6-2 6-0, and Bulgarian 10th seed Grigor Dimitrov led Donald Young 6-4 3-0 before the American retired.
Andy Murray will play Germany's Philipp Kohlschreiber after he beat Colombian qualifier Alejandro Falla 6-1 6-4.
Second seed Murray, who , will play his second-round match on Wednesday.