Djokovic, the Australian Open champion, was leading Dmitry Tursunov 6-2, 4-3 when the Russian retired with a right shoulder injury. The seventh-seeded Roddick defeated past Spaniard Feliciano Lopez 6-3, 6-4.
Ninth-seeded Argentine Juan Martin del Potro advanced to the round of 16 with a 6-0, 6-4 victory over Croat Mario Ancic and 16th-seeded Frenchman Gael Monfils beat Argentine qualifier Juan Monaco 6-4, 6-4.
Fernando Verdasco faced a stiff challenge from Tommy Robredo before advancing in three sets, 6-2, 6-7 (8-6), 6-2.
Also, Frenchman Florent Serra beat Argentine Guillermo Canas 4-6, 7-5, 6-3 and Swede Robin Soderling, who won in Lyon last week, beat Frenchman Josselin Ouanna 6-3, 6-4.
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