Juan Martin Del Potro serve sees off Ivo Karlovic

Juan Martin Del Potro served impeccably as he recorded a straight-sets win over Ivo Karlovic in the Sony Ericsson Open.

The Argentine lost only two points during his first five service games before breaking in the 11th game and then claiming the opening set.

He then broke in immediately at the start of the second set and comfortably held his advantage to take the match 7-5 6-4.

Del Potro hit six aces and won 89 percent of points behind his first serve.

The 11th seed will now face Marin Cilic in round three after the Croat saw off Igor Kunitsyn.