NEW YORK -- Rafael Nadal's first match as defending U.S. Open champion was hardly a tour de force.
He would fall behind in a set, then come back. Fall behind, then come back.
His serve was broken six times; that happened a total of five times in seven matches during his 2010 run to the title at Flushing Meadows. His shots didn't have their normal depth. He needed to save seven set points during the second set.
Locked in a struggle for nearly three hours, the second-seeded Nadal eventually got past 98th-ranked Andrey Golubev of Kazakhstan 6-3, 7-6 (1), 7-5 on Tuesday night to reach the second round of the U.S. Open.
"Well," Nadal conceded, "I was a little bit lucky to win today in straight sets."
That's for sure. And Nadal expended a lot more energy Tuesday than Novak Djokovic, who overtook the Spaniard at No. 1 in the rankings last month.
Indeed, it didn't take too long to see that Djokovic's right shoulder is feeling fine. He began his first-round match with a 121 mph service winner. Four points later, he closed that game with a 120 mph ace. He whipped forehands exactly where he wanted them. He returned well, too.
Playing his first match since Aug. 21, when he quit because of a sore and tired shoulder, the top-seeded Djokovic began setting aside any questions about his fitness for Flushing Meadows, building a 6-0, 5-1 lead before 197th-ranked qualifier Conor Niland of Ireland stopped after 44 minutes. Niland had food poisoning.
"Great opening performance," Djokovic declared. "Today I didn't feel any pain. I served well, and I played well, so I have no concern."
The 24-year-old Serb improved to 58-2 with nine titles in 2011, including at Wimbledon and the Australian Open. Djokovic is on his way to compiling one of the greatest seasons in tennis history, particularly if he can earn his first championship at the U.S. Open, where in the past four years he's lost twice in the final and twice in the semifinals.
"This year has been tremendous -- best so far in my career -- and there has been a lot of talk about history-making and this incredible run," said Djokovic, who lost to Nadal in last year's U.S. Open final but is 5-0 against him this season.
Nadal didn't enter the year's last Grand Slam tournament under the best of circumstances.
"His confidence is not too good," said Toni Nadal, Rafael's uncle and coach. "I hope in one week, it will be different."
After losing to Djokovic in the Wimbledon final, Nadal lost his first summer hard-court match at Montreal, then bowed out in the quarterfinals at Cincinnati, where he also burned two right fingers on a hot ceramic plate in a restaurant.
"I didn't have the best summer possible for me," said Nadal, whose second-round opponent is Nicolas Mahut, the man who lost the longest match in tennis history, 70-68 in the fifth set, at Wimbledon last year.
Against Golubev, who has a 3-13 career record in Grand Slam matches, Nadal trailed 3-2 in the first set, and 5-2 in each of the others.
"I hit good shots, but not enough," said Nadal, who finished with 18 winners, 23 fewer than Golubev.
There was one especially important point: At 5-all in the second set, Golubev hit a terrific drop shot with Nadal stuck behind the baseline. On a full sprint, Nadal lifted the ball over the net; Golubev flubbed an overhead to lose the point. Golubev thought the ball bounced twice -- which would have meant he won the point -- and argued at length with the chair umpire, but TV replays showed Nadal got there in time.
That gave Nadal a break point, which he converted to lead 6-5. He got broken yet again, but then reeled off the last six points of the tiebreaker.
Golubev served for the second set at 5-3, and for the third set at 5-2 and 5-4. Nadal broke each time.
"If you don't think about the points, it was not bad performance," Golubev said. "I mean, you have to win the points when you have to win -- for example, like second set or third set, when you serve for the set."
While Djokovic had no problems Tuesday, and Nadal overcame his, Day 2 of the tournament included a second consecutive first-round departure from the U.S. Open by the sixth-seeded French Open champion Li Na. Since becoming China's first major singles champion at Paris in June, Li has gone 5-6, exiting in the second round at Wimbledon, then losing 6-2, 7-5 to 53rd-ranked Simona Halep of Romania on Tuesday.
"Terrible feeling," Li said. "I really want to do well after Roland Garros. But, I mean, it's not easy to do. Always easy to say, 'I want to do, I would like to do,' but always lose early. Now I even lose all the confidence on the court. I was feeling, 'Oh, tennis just too tough for me.'"
It's the first time in 40 years that none of the women's champions at a season's first three Grand Slam tournaments reached the second round at the U.S. Open. Wimbledon champion Petra Kvitova lost her first-round match Monday, while Australian Open champion Kim Clijsters withdrew because of a stomach muscle injury.
The active leader for women's Grand Slam titles, Serena Williams, followed Nadal in Arthur Ashe Stadium on Tuesday night.
Earlier, top-seeded Caroline Wozniacki -- who's been ranked No. 1 for most of the past year but is still in search of Grand Slam trophy No. 1 -- defeated 125th-ranked Nuria Llagostera Vives of Spain 6-3, 6-1.
Afterward, Wozniacki was asked about criticisms that she lacks a big-time shot.
"They can say what they want," said Wozniacki, who is dating U.S. Open golf champion Rory McIlroy. "I'm the type of player I am."
Among the past major winners who advanced Tuesday were 2010 French Open champion Francesca Schiavone, who overcame 16 double-faults, including four in her last service game; 2008 French Open champion Ana Ivanovic, whose blood pressure was checked by a trainer at the final changeover and said afterward she felt overwhelmed while thinking about the recent death of her grandfather; and two-time Grand Slam champion Svetlana Kuznetsova.
Other winners included No. 4 Victoria Azarenka, No. 10 Andrea Petkovic, No. 11 Jelena Jankovic and three young Americans: Sloane Stephens, CoCo Vandeweghe and Vania King.
Two seeded men lost during the day: No. 16 Mikhail Youzhny was beaten by Ernests Gulbis of Latvia 6-2, 6-4, 6-4, and No. 32 Ivan Dodig was eliminated 6-7 (6), 6-3, 6-0, 2-6, 6-2 by Nikolay Davydenko of Russia, who was a U.S. Open semifinalist in 2006 and 2007 and once was ranked No. 3 but now is 39th.
Winners included No. 5 David Ferrer, No. 11 Jo-Wilfried Tsonga, No. 17 Jurgen Melzer and Americans James Blake and Donald Young.