Aside from one long, long game, Novak Djokovic kept things quick on a hot afternoon at the US Open.

The defending champion at Flushing Meadows dropped a 24-point, 15-minute game early in the second set, a tiny blip along the way to wrapping up another easy victory to reach the third round. He beat 112th-ranked Rogerio Dutra Silva of Brazil 6-2, 6-1, 6-2.

"Definitely doesn't feel great, spending 15 minutes for one game in this heat," Djokovic said.

Nevertheless, Djokovic finished with more than twice as many winners, 29, as unforced errors, 14. He needed a little more than 90 minutes all told to make sure he would keep intact his record of never having lost to a player ranked outside the top 100 at a major tournament.

"I didn't know much about my opponent. Never saw him play. So that could have been, you know, a difficulty at the start in order to figure out what his game plan is," Djokovic said. "But I have played well from the start to the end."

The second-seeded Serb has lost a total of seven games through two matches this year at the US Open.

"Obviously, I want to spend (as little) time as possible on the court," Djokovic said. "I have played a lot of tennis, a lot of matches, through the course of this summer."

That includes a runner-up finish to Rafael Nadal at the French Open, and a semifinal loss to eventual champion Roger Federer at Wimbledon, following a title at the Australian Open in January.

Dutra Silva, who never has reached the third round at a Grand Slam tournament, was impressed by Djokovic's play in Arthur Ashe Stadium.

"It's tough to hurt him. I tried, many ways, to hurt him. And actually I can't do that," Dutra Silva said with a smile. "I tried to play baseline. I tried to hit and hit the ball. I tried to play fast. It's so tough."

Djokovic won 37 of 41 points on first serves and never faced a break point all match.

Dutra Silva said that while Djokovic's first serves were hard to handle - the Serb did hit six aces - it was what happened once the ball was in play that was more problematic.

"When I put the ball in the court," Dutra Silva said, "I was in big trouble, you know?" 

Fourth seed David Ferrer also cruised into the third round with a 6-2 6-3 7-6 victory over Dutch qualifier Igor Sijsling.

The 30-year-old Spaniard sped through the first two sets and though he was tested hard in the third, he was always in control and clinched a convincing victory in two hours, seven minutes.

Ferrer, who reached the fourth round at Flushing Meadows a year ago, ran Sijsling ragged from the baseline as he raced to a two-sets lead in little over an hour.

World number 78 Sijsling raised his game in the third set and saved five match points but Ferrer won the tiebreak 14-12 to set up a match with former champion Lleyton Hewitt of Australia or Gilles Muller of Luxembourg.

Former champion Juan Martin del Potro was also in winning form, beating American Ryan Harrison  6-2, 6-3, 2-6, 6-2.

The 20-year-old Harrison, ranked 61st, was seeking to reach the third round at a Grand Slam event for the first time.

Each player faced 10 break points, but del Potro converted seven to three for Harrison. The American had 42 unforced errors.

-AP and Reuters