Rafael Nadal won his first match on the blue clay at the Madrid Open on Wednesday, defeating Nikolay Davydenko 6-2, 6-2 in the second round.

Nadal had little trouble on the surface that he criticised this week as soft and slippery, hitting six aces.

"I played much better than I expect,'' Nadal said.

"The (blue) court... doesn't make you feel comfortable. It's difficult, hard to attack and come back to defend. You just have to try and adapt.''

In the women's tournament, defending champion Petra Kvitova lost to Lucie Hradecka 6-4, 6-3.

Nadal, who broke his Russian opponent four times to advance to the third round, will next meet Fernando Verdasco. The Spaniard defeated Alejandro Falla of Colombia 6-7 (4), 6-4, 6-4.

Third-ranked Roger Federer will play his opening match later on Wednesday against Milos Raonic of Canada.

Kvitova struggle

Also, Marin Cilic beat John Isner 7-6 (4), 7-6 (3) and fifth-seeded David Ferrer advanced by beating Radek Stepanek 7-6(4), 6-2.

"It has nothing to do with the courts, I just didn't play well,'' said Isner, who praised his Croatian opponent.

"He has played better and he deserves to win.''

Other men's winners on Wednesday included Stanislas Wawrinka of Switzerland, Alexandr Dolgopolov of Russia and French pair Gael Monfils and Richard Gasquet.

The third-seeded Kvitova struggled with her serve against Hradecka. Kvitova was broken five times by Hradecka of Czeck republic, who will face Ekaterina Makarova in the third round. Makarova beat Maria Kirilenko of Russia 6-4, 6-4 to advance.

Li Na of China and Samantha Stosur of Australia both reached the quarterfinals along with Agnieszka Radwanska, who routed Sara Errani 6-0, 6-1 and ended the Italian's 16-match winning streak.

Errani failed to convert any of her eight break points as she showed little of the consistent play that carried her to three straight titles this season.

Radwanska will next face Roberta Vinci following her 6-1, 6-2 victory over Yanina Wickmayer of Belgium.