US Open: Novak Djokovic beats Rogerio Dutra Silva in round two

Novak Djokovic continued the defence of his US Open title with a routine straight-sets victory over Brazil's Rogerio Dutra Silva.

Second seed Djokovic, of Serbia, took just one hour and 39 minutes to secure a 6-1 6-2 6-1 second-round win.

Andy Roddick's retirement plans are on hold after the American comfortably beat Bernard Tomic 6-3 6-4 6-0.

Spain's David Ferrer, the number four seed, overcame Dutch qualifier Igor Sijsling 6-2 6-3 7-6 (14-12).

Djokovic has spent less than three hours on court in winning his first two matches, having eased past Italy's Paolo Lorenzi on Tuesday.

The Serbian said: "I didn't know much about my opponent; I'd never seen him play.

"Even if the scoreline doesn't indicate it, it was a tough match. I played well from the start to the end."

Roddick, who announced this week that he will retire at the end of the tournament, was cheered by a patriotic New York crowd when he walked on court at Arthur Ashe Stadium.

The spectators were on their feet at the end of the match, applauding the former world number one's dominant 87-minute victory over Australian teenager Tomic.

Roddick admitted he struggled to control his emotions when he watched a television feature about his career before the match.

"It got to me a little bit. I had to get away from that," said the 30-year-old, who hit 10 aces and 24 winners to book a third-round meeting with Italy's Fabio Fogini.

"That was a different kind of nerves than I've had before."

Tomic was accused of not trying by seven-time Grand Slam winner and TV commentator John McEnroe, and became involved in an angry exchange with a journalist at the post-match news conference.

Asked about McEnroes's comments, Tomic said: "He's probably right."

But when pressed, he responded: "That's how I play. If you think that's that, it's up to you. What is your name?" When the reporter told him, Tomic replied: "I'll remember you."

Serbia's Janko Tipsarevic, the number eight seed, beat American Brian Baker 6-4 6-3 6-4.

However, the home fans at Flushing Meadows were lifted by a second-round win for American college champion Steve Johnson.

Johnson, a 22-year-old wildcard, saw off Latvia's Ernests Gulbis 6-7 (3-7) 7-6 (7-5) 6-3 6-4 to become the first college champion to reach the third round of the US Open since Sargis Sargsian in 1995.

He will play Richard Gasquet, the 13th seed, in the third round after the Frenchman beat Bradley Klahn 6-3 6-3 6-1.

John Isner was another American to progress, the ninth seed negotiating a second-set wobble to overcome Jarkko Nieminen 6-3 6-7 (5-7) 6-4 6-3.

Seventh seeded Argentine Juan Martin del Potro, the 2009 champion, beat American Ryan Harrison 6-2 6-3 2-6 6-2, while former world number one Lleyton Hewitt set up a third-round meeting with Ferrer thanks to a battling 3-6 7-6 (7-5) 6-7 (5-7) 7-5 6-4 victory over Gilles Muller.

Alexandr Dolgopolov saw off Marcos Baghdatis 6-4 3-6 6-0 7-6 (7-5) and will play Stanislas Wawrinka, the 18th seed, in the third round after the Swiss overcame Belgium's Steve Darcis 6-7 (6-8) 6-3 4-6 6-1 7-5.

Meanwhile, Wimbledon champions Jonathan Marray and Frederik Nielsen were knocked out of the men's doubles.

Britain's Marray and Denmark's Nielsen, the number 11 seeds, lost 6-1 6-7 (6-8) 6-4 to Jesse Levine of the United States and Marinko Matosevic of Australia.