Djokovic untroubled by Benneteau to continue U.S. Open title defense

(CNN) -- Serbia's Novak Djokovic cruised into the fourth round of the U.S. Open Sunday as he dispatched Frenchman Julien Benneteau in straight sets.

Djokovic won 6-3 6-2 6-2 in the first match on the Arthur Ashe Stadium court -- not facing a single break point in a 97-minute victory.

He put that down to improvements he has made with his service and the work appeared to have paid off.

"I wanted to get more free points on the first serve and today it was working well," Djokovic told the official tournament website.

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"I know that I cannot serve more than 130 mph, though I'm working on it, so I hope to place it well."

Djokovic's first breakthrough came in the sixth game of the first set when he broke his opponent for the first time and the next two sets proved easier for the second seed.

The 25-year-old Djokovic will play Ukrainian 14th seed Alexander Dolgopolov, who dispatched Stanislas Wawrinka of Switzerland in straight sets.

Home favorite Andy Roddick, playing in his final tournament, is looming as a possible quarterfinal opponent for Djokovic.

The 20th seed scored a convincing 7-5 7-6 4-6 6-4 victory over Italy's Fabio Fognini, but he will have to get past the imposing figure of 2009 champion Juan Martin Del Potro of Argentina to reach the last eight.

Del Potro beat compatriot Leonardo Mayer in straight sets to reach the fourth round.

Spanish fourth seed David Ferrer also went through to the second week as he ended the run of former world number one Lleyton Hewitt of Australia, 7-6 4-6 6-3 6-0.

Ferrer breezed through the final two sets after the 2001 champion Hewitt leveled at a set all.

He will face either French 13th seed Richard Gasquet or U.S. collegiate champion Steve Johnson, who were playing later at Flushing Meadows.