New York, NY

American Andy Roddick temporarily put retirement on hold after beating Italy's Fabio Fognini, 7-5, 7-6 (1), 4-6, 6-4, Sunday to advance to the last 16 of the US Open.

"I'm new at this," said Roddick, who won his only Grand Slam title here in 2003. "I don't have a lot of questions for how, why and when right now. I was just trying to play point-for-point. I'm trying to keep my emotions together, all the while trying to appreciate this tournament."

The 20th ranked Roddick, who announced his intention to retire after the US Open Thursday, will eye his ninth career quarterfinal appearance at Flushing Meadows against 2009 US Open champion Juan Martin del Potro of Argentina, who defeated countryman Leonardo Mayer 6-3, 7-5, 7-6 (9).

"You just keep going -- what else do I have to do?" said Roddick on the prospects of beating del Potro. "I'm going to give it my all here."

Defending champion Novak Djokovic of Serbia marched into the fourth round after making quick work of Frenchman Julien Benneteau en route to a 6-3, 6-2, 6-2 victory.

The Serbian unleashed 13 aces and took advantage of Benneteau's 22 unforced errors to finish the match in one hour and 37 minutes.

"I felt from the start that from the baseline, you know, I was very comfortable, defense, offense, in that position," Djokovic said. "So I tried to, you know, be aggressive and not allow him to come to the net because, you know, he plays good when he's in control."

"I wanted to get more free points on the first serve and today it was working well," Djokovic added. "I know that I cannot serve more than 130 mph, though I'm working on it, so I hope to place it well."

Djokovic broke Benneteau for the first time to take a 4-2 lead in the first set before ending it in 34 minutes. He later used the momentum of his first-set win to break Benneteau in the first game of the second set and held serve to take a 2-0 lead.

In the next round, Djokovic will face Stanislas Wawrinka, who defeated Alexandr Dolgopolov in straight sets, 6-4, 6-4, 6-2.

Meanwhile, fourth seed David Ferrer advanced to his 10th straight fourth round at a Grand Slam event after beating defeat wild card and 2001 champion Lleyton Hewitt 7-6(9), 4-6, 6-3, 6-0.