Petra Kvitova was the shock casualty at the Madrid Open on Wednesday, the reigning champion dumped out by qualifier Lucie Hradecka in the second round.

Petra Kvitova 12134213423 - Defending champ Kvitova crashes out in Madrid

The 2011 Wimbledon champion, seeded No. 3 in Spain, only managed to claim six of the 24 points on her second serve, which ultimately led to the Czech's downfall.

It was another disappointing performance from Kvitova, who struggled to hold her serve throughout the contest despite hammering five aces, as her wait for a first title of the year continues.

Sixteenth seed Maria Kirilenko was also a shock loser, losing in straight sets to Ekaterina Makarova.

Fourth seed Agnieszka Radwanska, who is searching for her third title of the year, had no such worries, crushing Sara Errani 6-0 6-1. Errani was bidding for a 17th consecutive clay-court win but she found the world No. 3 in an uncharitable mood - Radwanska breaking the Italian five times.

There was another one-sided contest in the match between Roberta Vinci and Yanina Wickmayer, with the former winning through 6-1 6-2 in less than an hour.

In the third round, fifth seed Sam Stosur, yet to find the form this season that took her to the US Open title last year, chalked up a morale-boosting win over Petra Cetkovska. The Australian saved seven of the eight break points she faced en route to a 6-3 6-2 success. China's Li Na battled past Angelique Kerber 7-5 6-4 to book her place in the next round, keeping alive her dream of reaching a first final in Madrid.

The No. 1 seed Victoria Azarenka was given a workout by Ana Ivanovic but she was able to secure a 6-4 6-4 win in the third round.