Rafael Nadal's first match as defending US Open champion was hardly a tour de force, with the Spaniard lucky to record a victory over the relatively lowly-ranked Andrey Golubev on Tuesday.

Nadal dropped serve six times, an extraordinary figure given he was only broken five times across seven matches en route to winning the 2010 title at Flushing Meadows. His shots didn't have their normal depth and he needed to save seven set points during the second set before coming through 6-3, 7-6 (1), 7-5.

"I was a little bit lucky to win today in straight sets," Nadal said.

Still, he progressed to the second round and a clash with Frenchman Nicolas Mahut, who recovered from two sets down to beat Robert Farah.

Nadal certainly expended more energy than Novak Djokovic, who overtook the Spaniard at No. 1 in the rankings last month.

Playing his first match in nine days as he rested a sore right shoulder, the top-seeded Djokovic began setting aside any questions about his fitness for Flushing Meadows, building a 6-0, 5-1 lead before qualifier Conor Niland of Ireland stopped after 44 minutes due to the effects of food poisoning.

No concern

"Great opening performance," Djokovic declared. "Today I didn't feel any pain. I served well, and I played well, so I have no concern."

Nadal's Spanish compatriot David Ferrer, seeded fifth, also had to work hard to beat Igor Andreev of Russia, 2-6, 6-3, 6-0, 6-4. Ferrer will next meet American James Blake, who got past Jesse Huta Galung in four sets.

Russia's Mikhail Youzhny and Croatia's Ivan Dodig were the seeded casualties. Youzhny was beaten 6-2, 6-4, 6-4 by Latvia's Ernests Gulbis, while Dodig came out on the wrong end of a topsy-turvy match against Russia's Nikolay Davydenko, who prevailed 6-7 (6), 6-3, 6-0, 2-6, 6-2.

In the women's draw, top seed Caroline Wozniacki had a comfortable 6-3, 6-1 win over Spain's Nuria Llagostera-Vives and will next take on Arantxa Rus, who was a straight sets winner over Elena Vesnina.

Belarussian Viktoria Azarenka, seeded fourth, was a 6-1, 6-3 winner over Sweden's Johanna Larsson and her second-round opponent will be Argentine Gisela Dulko, who won in straight sets against Canada's Rebecca Marino.