The Serb notched up his 22nd consecutive win this year after winning three tournaments this year, including the Australian Open and January and last week’s BNP Paribas Open in Indian Wells.
He will next play Victor Troicki for a place in the quarter-finals. Djokvoic beat Troicki for the loss of just one game on his way to the title in Indian Wells last week.
In other matches, fourth see Robin Soderling of Sweden was knocked out of the tournament by Juan Martin Del Potro of Argentina who is continuing his run of impressive form since coming back from injury. Del Potro beat Soderling in straight sets, 6-4 6-3 and will now face American Mardy Fish who put out Frenchman Richard Gasquet 6-4 6-3.
Andy Murray's conqueror Alex Bogomolov Jr of America was defeated by compatriot John Isner 6-2 7-6 (7-4).
