Serena Williams won the gold at the London Olympics and got her 2012 U.S. Open off to a fine start. Reuters

(Reuters) - Defending champion Novak Djokovic and three-times winner Serena Williams each dropped just two games against bewildered opponents at the U.S. Open on Tuesday, leading a procession of top seeds into the second round of the year's final grand slam.

Joining Djokovic in the winner's circle at Flushing Meadows were number five Jo-Wilfried Tsonga, number six Tomas Berdych, and former champion Andy Roddick, the 20th seed.

On the women's side, former world number one Caroline Wozniacki was a first round casualty while second seed Agnieszka Radwanska and number six Angelique Kerber advanced easily.

Djokovic took just an hour and 13 minutes to blitz Italy's Paolo Lorenzi 6-1 6-0 6-1 in his first-round match under the lights on a cool evening at Arthur Ashe Stadium.

The charismatic Serb's win was so one-sided that it was difficult to tell if the 2011 U.S. Open champion was that good or Lorenzi had perhaps the worst evening of his life on a tennis court.

"My game was great from the start to the end," said the second seeded Djokovic, who won three of four majors last year.

"It's also important for me to try to be as economical with the time I spend on the court as possible, but obviously not underestimating any opponent.

"I played really focused, tried to get to the net also. It was great all in all."

The 69th-ranked Lorenzi said he had trouble with the blustery conditions before a sell-out crowd of nearly 24,000 at cavernous Ashe Stadium.

"I had never played on the center court and there was a lot of wind," he said. "So sometimes I'd miss an easy ball because the ball was flying a lot. But he's playing so good. I tried my best."

Fourth-seeded Williams followed Djokovic on the court and produced a 6-1 6-1 rout of 75th-ranked American Coco Vandeweghe, who committed 22 errors and produced only nine winners against the 30-year-old, 14-times grand slam champion.

Williams said the conditions were tough on both players.

"I usually gauge the wind by my hair," she said. "If it's really going forward, I'm thinking, 'It's really windy.'

"It was really gusty, so at some points it would be really windy, at some points it wouldn't be ... I didn't hit anything too hard because the ball, I wouldn't have known where it was going to go."

World number two Radwanska of Poland showed no signs of a shoulder injury that forced her out of the New Haven tournament last week as she routed 91st-ranked Nina Bratchikova 6-1 6-1.


Hampered by a knee problem, eighth-seeded Wozniacki never broke the serve of world number 96 Irina-Camelia Begu of Romania and lost 6-2 6-2.

"You always want to go in and do your best no matter what's happening out there," Wozniacki said softly. "I tried. I didn't play particularly well, made too many errors.

"It's unfortunate because it's a huge tournament, a tournament you want to play well in."

Venus Williams overpowered Bethanie Mattek-Sands 6-3 6-1 and in the process clocked the fastest women's serve of the tournament to date at 124 mph.

Now ranked number 46, Venus said she yearned to get back into the world top 10 but conceded "it never happens the way you want it to."

"That's one thing I found out throughout my whole career," said Venus, who was forced to withdraw from the tournament shortly before her second-round match last year after discovering she had an auto-immune disease.

"When you don't make it to one goal, just make some more. But, of course, I'm looking forward to the top 10, all that great stuff. I feel like I have it in me."

Like Venus, Roddick is trying to re-capture the form that saw him win the U.S. Open in 2003. On Tuesday, he cruised past 21-year-old American qualifier Rhyne Williams 6-3 6-4 6-4.

Roddick said "the game has gotten significantly better" than when he won the title.

"I had a massive serve at 135 (mph), and this kid today was hitting them that big," he said with a smile.