Sorribes Tormo is the only home player through to the third round of the Women's Tennis Association (WTA) 1000 event, following a 6-3, 6-1 victory over four-time Grand Slam winner Naomi Osaka.

Japan's Osaka, who appeared to be struggling with a leg complaint, was broken five times en route to defeat.

Next up for Sorribes Tormo will be Daria Kasatkina, who stunned fourth seed Maria Sakkari.

The Greek took the first set but was made to pay for being profligate when break opportunities arose, with Kasatkina fighting back to win 3-6, 6-3, 6-1.

Sakkari forced six break points but converted just one.

Kasatkina is Russian, but allowed to compete as a neutral under WTA Tour rules.

Ukraine's Anhelina Kalinina beat seventh seed Muguruza in straight sets to set up a meeting with US Open champion Emma Raducanu.

Britain's Raducanu defeated Kalinina's compatriot Marta Kostyuk 6-2, 6-1 in a battle of 19-year-olds.

Canadian Bianca Andreescu, a former US Open winner, brushed aside the American sixth seed Danielle Collins 6-1, 6-1.

Today's results mean Tunisian Ons Jabeur is the top seed remaining at number eight.

The men's first round also began at the Madrid Open today, with Britain's Dan Evans and American John Isner among the victors.

No seeds were in action.