MADRID (AP) -- Second-seeded Simona Halep and Venus Williams both lost in the opening round of the Madrid Open on Sunday, while top-seeded Serena Williams had a trouble-free debut.
Defending champion Maria Sharapova also advanced after beating Timea Bacsinszky 6-2, 6-3.
Halep, a finalist both in Madrid and at the French Open last year, failed to convert two set points in the first set before losing 7-6 (6), 6-3 to Alize Cornet of France.
Serena Williams defeated American Madison Brengle 6-0, 6-1 after breaking her six times to wrap her 24th straight win in less than an hour. She will face Sloane Stephens next on Tuesday.
''I don't think I've played her on clay yet,'' Williams said about Stephens, who beat her at the 2013 Australian Open. ''We had a really tough three-set match the last time we played. She's playing really well. She's moving well and is having a better year this year. I think she's kind of flying under the radar.''
Venus Williams, however, lost to fellow former No. 1 Victoria Azarenka 6-3, 7-5.
Venus Williams, seeded 16th, went up a break at 4-3 in the second set, only for Azarenka to win four of the next five games.
Also, Barbora Strycova of the Czech Republic came back from a 3-0 deficit in the second set to oust sixth-seeded Eugenie Bouchard, 0-6, 6-3, 6-3. Samantha Stosur served 14 aces to eliminated 12th-seeded Angelique Kerber, 4-6, 6-3, 6-3.
Petra Kvitova, seeded fourth, rallied past qualifier Olga Govortsova, 3-6, 6-1, 6-4, and fifth-seeded Caroline Wozniacki brushed aside Jarmila Gajdosova, 6-3, 6-0.
Other seeded winners included Carla Suarez Navarro, Andrea Petkovic, Karolina Pliskova and Sara Errani.
The men's tournament only had two first-round matches.
Juan Monaco beat Nicolas Almagro 6-3, 6-2, while Simone Bolelli eliminated Kevin Anderson 6-4, 6-3.