MADRID — Venus Williams lost to Anett Kontaveit of Estonia in the first round of the Madrid Open on Saturday.

Kontaveit rallied from a set down to beat the eighth-seeded Williams 3-6, 6-3, 6-2 on the outdoor clay court.

"I'd lost to her two times already, and so I had nothing to lose," Kontaveit said. "I didn't go out there feeling scared. I do feel like I can challenge anybody here, so I was feeling good to go on the court."

Kontaveit was coming off a semifinal run in Stuttgart last week. Williams was playing her first clay match of the year, though she has passed the second round only once in Madrid.

Fourth-seeded Elina Svitolina beat Alize Cornet 6-2, 6-2 after breaking her serve five times.

Irina-Camelia Begu beat fifth-seeded Jelena Ostapenko 6-3, 6-3, and Kristina Mladenovic also upset 12th-seeded Coco Vandeweghe 7-5, 6-0.

Sixth-seeded Karolina Pliskova and seventh-seeded Caroline Garcia advanced.

Two-time defending champion and top-ranked Simona Halep opens on Sunday, along with Gabrine Muguruza, Caroline Wozniacki and Maria Sharapova.