Venus Williams rolled back the years to beat Belgium's Kirsten Flipkens in the first round of the U.S. Open on Monday as the final grand slam of the year burst into life.

Roared on by an energetic New York crowd on a blustery day at Flushing Meadows, Williams showed no signs of the back problems that have sidelined her for most of the year as she demolished her younger opponent 6-1, 6-2.

The 33-year-old American, the second oldest player in the women's singles draw, provided a glimpse of the form that saw her win the U.S. Open in 2000 and 2001 as she romped to victory in just one hour and 24 minutes.

"It's good to be back," she said.

Williams has only played 18 matches this year and slipped to 60th place in the world rankings while Flipkens is enjoying the best season of her career.

The 27-year-old made the semi-finals at Wimbledon in July, her best result at any grand slam, and was seeded 12th for the U.S. Open. Earlier this month, she beat Williams in Toronto after losing the first set 6-0.

"I was glad to close it out today," said Williams, whose younger sister Serena was scheduled to play her opening match on the center court later on Monday.

Flipkens was the first notable casualty in a wide open women's draw that promises to be one of the most competitive in years.

China's Li Na, the 2011 French Open champion and runner-up in Australia this year, needed just 64 minutes to crush Olga Govortsova of Belarus 6-2 6-2.

Poland's Agnieszka Radwanska, the third seed, was even more ruthless, thumping Spain's Silvia Soler-Espinosa 6-1, 6-2 in 63 minutes in the opening match on the center court.

There was an early upset in the men's draw when Japan's Kei Nishikori, Asia's highest-ranked man, was beaten by British qualifier Dan Evans.

The Englishman, ranked 179th, stormed to a 6-4, 6-4, 6-2 win over the 11th seed to set up a second round meeting with combative Australian Bernard Tomic, who won a five-set slugfest with Spain's Albert Ramos.

"It's definitely a good one," said Evans, playing in his first U.S. Open. "That was pretty good out there to play so well and against someone so highly ranked."

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