Djokovic battles to tough win in Madrid

The world number 137 shocked the Serbian by breaking him twice to level the match in a stunning second set, but Djokovic recovered with the crucial final-set break to win 6-2 2-6 6-3 in one hour and 46 minutes.

In the day's other men's second-round match, sixth seed Tomas Berdych also advanced as he held off big-serving South African Kevin Anderson for a 6-4 6-3 success.

In the first round, 13th seed Feliciano Lopez was the only seeded casualty as he fell 3-6 7-6 (8/6) 6-4 to Austria's Jurgen Melzer, while recent Bucharest winner Gilles Simon was pushed in a 6-7 (7/1) 6-3 6-3 win over Italy's Fabio Fognini.

Other seeds to advance were 14th seed Richard Gasquet, who needed a final-set tie-break to see off Brazil's Thomaz Bellucci 4-6 6-4 7-6 (7/5), Juan Martin Del Potro, Alexandr Dolgopolov, Gael Monfils and Fernando Verdasco.

Veteran Czech Radek Stepanek surprised Australian youngster Bernard Tomic 6-2 7-5 and there were also wins for Marin Cilic, Milos Raonic, Andreas Seppi, Marcel Granollers, Federico Delbonis and Stanislas Wawrinka.

In the women's event, Serena Williams continued her impressive start to the clay-court season as the American ninth seed brushed aside Anastasia Pavlyuchenkova of Russia 6-2 6-1 in just 61 minutes.

Top seed Victoria Azarenka beat Czech qualifier Andrea Hlavackova 6-4 7-6 (7/2) and second seed Maria Sharapova saw off another Czech player, Klara Zakopalova, 6-4 6-3.

Sixth seed Caroline Wozniacki progressed with a 6-4 7-6 (7/2) win over Germany's Mona Barthel, and 13th-seeded Serb Ana Ivanovic also had few problems dispatching Russia's Nadia Petrova 7-5 6-1.

Qualifier Varvara Lepchenko continued her good form by upsetting Israeli Shahar Peer 7-6 (7/2) 6-4 while there were also wins for Anabel Medina Garrigues and Lucie Safarova.