MADRID - NOVAK Djokovic eased past Oscar Hernandez 6-3, 6-3 on Wednesday to advance to the third round of the Madrid Open.

The third-seeded Serb fell awkwardly on his right knee on the clay surface at Madrid's new 'Magic Box' tennis center early in the second set, but was rarely troubled by his Spanish opponent before closing out the match in 1 hour, 38 minutes.

Djokovic never faced a break point in the match, while breaking Hernandez once in the first set and twice in the second.

Juan Martin del Potro of Spain also advanced to the third round when Tomas Berdych was forced to retire with a leg injury.

The Czech player, who won his first title of the year at the BMW Open in Munich on Sunday, retired while trailing 6-2, 4-1.

In the women's event, seventh-seeded Victoria Azarenka of Bulgaria eased past Peng Shuai of China 6-4, 6-1 and Vera Dushevina of Russia beat Italy's Francesca Schiavone 6-3, 4-6, 6-2.

In later matches, top-seeded Rafael Nadal was due to meet Austria's Jurgen Melzer, while women's No. 1 Dinara Safina was set to play Li Na of China. -- AP