Australian Open champion Angelique Kerber was dumped out of the Madrid Open in the first round by Czech Barbora Strycova 6-4, 6-2 on Sunday.
Kerber had travelled to the Spanish capital in fine form having retained her title in Stuttgart last week.
However, the second seed was outplayed by the world number 33 Strycova, who she had beaten 6-1, 6-1 in Miami back in March.
“I’d win four games in the matches we played before,” said Strycova.
“I went into this match thinking I had nothing to lose. I mean, it can’t be worse than Miami.”
Kerber’s defeat means Garbine Muguruza is the highest seed left in the bottom half of the draw, and the Spaniard sealed her place in round two with a 6-2, 7-5 win over Anna Schmiedlova.
“Of course I was a little bit nervous and tense because the first matches are always complicated,” said Muguruza, who is aiming to be the first Spanish woman to win the title in Madrid.
“In Madrid we have this extra pressure because I’m here at home. Perhaps you’re a little bit more nervous because of that, but my first feeling is that I’m satisfied for winning the match.”
Victoria Azarenka stretched her winning streak to 15 matches after winning in Indian Wells and Miami as she overcame some stiff first set resistence from Britain’s Laura Robson to win 6-4, 6-2.
Azarenka could meet defending champion Petra Kvitova in the quarter-finals as the Czech had no trouble in disposing of Lara Arrubarrena 6-3, 6-2.
US Open finalist Roberta Vinci is out after losing in straight sets to Montenegran Danka Kovinic 6-4, 6-2.
German Laura Siegemund continued her great start to the clay-court season after reaching the Stuttgart final as a qualifier as she dumped out ninth seed Svetlana Kuznetsova 6-0, 3-6, 6-3.
Eighth seed Carla Suarez Navarro came from a set down to beat Hungary’s Timea Babos 3-6, 6-2, 6-3.
Ana Ivanovic also had to go the distance to see off Katerina Siniakova 6-3, 3-6, 6-4.