Defending US Open Men's Singles Champion Rafael Nadal of Spain takes part in the draw ceremony for the 2011 US Open Tennis Championships at the Billy Jean King National Tennis Center in New York, Aug 25, 2011. [Photo/Agencies]

Novak Djokovic faces the daunting prospect of possibly having to beat Roger Federer and Rafa Nadal to win the US Open for the first time and end the year as the world number one.

The Serbian has already won this season's Australian Open and Wimbledon titles and is the overwhelming favourite to win the last grand slam of 2011, starting at Flushing Meadows on Monday, to wrap up the top spot for the end of year rankings.

But a niggling shoulder injury that forced him to quit last weekend's Masters final in Cincinnati, has raised questions about his fitness, especially with his foes lurking ominously at the business end of the tournament after the official draw was conducted in New York on Thursday.

Djokovic was drawn to launch his tournament against an as yet unknown qualifier but if results go according to the rankings, the top seed will face a tricky last weekend, when the semi-finals and final will be played on successive days.

His projected semi-final opponent is five-time US Open champion and third seed Federer, who faces Colombia's Santiago Giraldo in the first round.

If Djokovic can beat the most prolific male grand slam winner of all time, his opponent in the final could be either Nadal, who beat him in last year's final, or the in-form Briton Andy Murray.

"Last year was a very emotional time for me, because I completed all my grand slams," Nadal said at Thursday's draw after the second seeded Spaniard was drawn to face Kazakhstan's Andrey Golubev first up.

"It was very tough but I played some of my best tennis in the final (against Djokovic) and I known I can do well."

Djokovic is not the only top player with concerns. Nadal has been battling blisters and Federer has not won a grand slam in nearly two years.

Former world number one John McEnroe, speaking on American television network ESPN, said he was tipping Murray to win the men's singles title.

The fourth-seeded Scotsman is the only player in the top four who has yet to win a grand slam but has been in great form during the US hardcourt season. His first round opponent is Somdev Devvarman of India.

"The hungriest guy out there should be Andy Murray," McEnroe said. "This is his best chance ever to win a major."

McEnroe said he would be surprised if anyone outside the top four won the title but he nominated towering Argentine Juan Martin Del Potro as the most likely to cause an upset.

Del Potro won the US Open two years ago, beating Federer in the final, but was unable to defend his title last year because of an injury. He makes his return this year against Italian Filippo Volandri.