NEW YORK, USA (AFP) — All-conquering Novak Djokovic found the going even easier than expected at the US Open yesterday, as food poisoning hampered the challenge of first-round opponent Conor Niland.

The qualifier from Ireland, ranked 197th in the world, wasn’t expected to pose much problem for Djokovic, who has surged to the top of the world rankings with nine titles this season — including two Grand Slams.

But a bout of food poisoning that lingered from Sunday morning had left the 29-year-old Niland physically weakened, and Djokovic needed just 44 minutes to take a 6-0, 5-1 lead before Niland called it a day.

The quick match may prove a boon for Djokovic, who suffered just his second defeat of the season when he retired from the Cincinnati final against Andy Murray this month with a sore shoulder.

Djokovic was part of a stellar line-up on the Ashe court yesterday along with women’s world number one Caroline Wozniacki, defending men’s champion Rafael Nadal and 13-time Grand Slam champion Serena Williams.

Wozniacki cruised into the second round with a 6-3, 6-1 victory over 125th-ranked Nuria Llagostera Vives.

While the top-seeded Dane is keen to claim a maiden Grand Slam title, she again bristled at suggestions that she needs a major crown to validate her number one status.

But the fact remains that while Wozniacki has consolidated her spot atop the rankings with half-a-dozen titles this season — the most recent at New Haven on Saturday — she has flopped in Grand Slams, with a semi-final exit in Australia, a third-round defeat at Roland Garros and a fourth-round loss at Wimbledon.

Since then she suffered early exits at Bastad, Toronto and Cincinnati and dropped her father Piotr as her coach.

Wozniacki looked good against Llagostera, breaking her for the fourth time to seal the victory and facing just one break point in the match.

Fourth-seeded Victoria Azarenka of Belarus also advanced with ease, beating Sweden’s Johanna Larsson,

6-1, 6-3.

Williams is seeded just 28 here, after a rankings slide due to her nearly year-long absence with a series of health problems.

Williams has nevertheless stamped herself a favourite with two hardcourt victories in the build-up to the Open, and her potential third-round clash with Azarenka was the talk of the draw last week.

In other early matches, Spanish fifth seed David Ferrer rallied to reach the second round with a 2-6, 6-3, 6-0, 6-4 victory over Russian Igor Andreev.

French 11th seed Jo-Wilfried Tsonga, who missed the US Open last year with a knee injury, returned with a 6-4, 6-4, 6-4 victory over Taiwan’s Lu Yen-Hsun.

Wimbledon semi-finalist Sabine Lisicki of Germany romped to a 6-3, 6-3 victory over Alona Bondarenko in just 70 minutes.

Lisicki, who arrived in New York fresh from a WTA triumph in Dallas on Saturday, booked a second-round clash with two-time US Open champion Venus Williams.