Defending champion Novak Djokovic needed only 99 minutes to win and didn't face a single break point as he beat Rogerio Dutra Silva at the U.S. Open on Friday, breezing into the third round.

As Djokovic blasted past the Brazilian, three other former champions also advanced: Andy Roddick, Juan Martin del Potro and Lleyton Hewitt.

Roddick, having announced this tournament will be his last, dominated Australian Bernard Tomic 6-3, 6-4, 6-0, ensuring his career stretches into at least one more match.

Asked whether he got emotional while preparing for what could have been his final appearance, Roddick said: "I've been trying to be good all day. Had a rough patch there, about 15 minutes before the match. Made the mistake of walking by one of the TVs while they were doing slow, dramatic things. I assume it was set to an '80s ballad. It got me a little bit."

Not only was Tomic outclassed, but by the late stages, TV commentator and seven-time major champion John McEnroe said the Australian maybe should be fined for lack of effort.

Tomic initially responded casually, saying: "He's probably right."

But when pressed some more, Tomic bristled at a reporter and said, "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."

Del Potro downed Ryan Harrison of the United States, 6-2, 6-3, 2-6, 6-2 while Hewitt — who is playing on a wild card due to his low ranking — showed his trademark grit to outlast Gilles Muller of Luxembourg, 3-6, 7-6 (5), 6-7 (5), 7-5, 6-4.

David Ferrer, the fourth seed and perennial nearly man of recent years behind the big four of men's tennis, also progressed to round three by beating Igor Sijsling of the Netherlands, 6-2, 6-3, 7-6 (12).

Among the other leading men's seeds, Janko Tipsarevic comfortably beat Brian Baker of the United States, 6-4, 6-3, 6-4 while leading local hope John Isner suffered a rare tiebreaker loss but still defeated Finnish veteran Jarkko Nieminen 6-3, 6-7 (5), 6-4, 6-3.

On the women's side, the main upset was Laura Robson beating China's Li Na 6-4, 6-7 (5), 6-2. Having ended the career of Kim Clijsters in the previous round, Britain's Robson can make it a hat trick over former grand slam tournament winners when she faces defending champion Sam Stosur in the next round.

"I have had a fairly tough draw, haven't I?" Robson said.

Ranked 89th, Robson had never been past the second round of a major tournament or knocked off a top 10 opponent before this year's Open.

"I have had lots of tough matches against some very experienced opponents, so the way that I see it, it was time to start winning a few of them," Robson said.

The seventh-seeded Stosur was pushed for the first time in this year's Open by No. 31 seed American Varvara Lepchenko, but the Australian dominated the second set for a 7-6 (5), 6-2 victory.

Stosur has never faced Robson — or really watched her play for long.

"She's full of confidence and had two very, very good wins," Stosur said.

World No. 1 Victoria Azarenka kept up her imperious form by sweeping past Zheng Jie of China 6-0, 6-1 to move into the fourth round. The Belarussian has lost only six games over her three matches.

Four-time major champ Maria Sharapova, the No. 3 seed, ended the surprise run of Mallory Burdette, needing 58 minutes to win 6-1, 6-1. Fifth-seeded Petra Kvitova, the 2011 Wimbledon champ, also advanced with a 6-4, 6-4 win over France's Pauline