Defending champion Petra Kvitova has been upset by qualifier and Czech compatriot Lucie Hradecka in straight sets in the second round of the Madrid Open tennis tournament.
World number one Victoria Azarenka, who lost to Kvitova in last year's final of the premier clay event, claimed her place in the quarter-finals with a straight sets win over Ana Ivanovic of Serbia.
Belarussian Azarenka, winner of four titles this year including her first grand slam singles at the Australian Open, needed four match points to finish off a stubborn Ivanovic and will play China's Li Na for a place in the semi-finals.
Li, the French Open champion and eighth seed, beat 12th-seeded German Angelique Kerber.
There were also wins for Samantha Stosur and Agnieszka Radwanska.
