INJURY WORRIES FOR TOP THREE

 Roger Federer
Novak Djokovic, Rafael Nadal and Roger Federer face a worrying power shortage at the U.S. Open as injury and faltering form plague the brightest lights of tennis's new golden age.

World No. 1 Djokovic, the hottest player in 2011 with a 57-2 winning record, was forced to quit the Cincinnati Masters final against Andy Murray when his weary right shoulder betrayed him.

Defending U.S. Open champion Nadal, who completed the career Grand Slam with his victory in 2010, has endured a torrid summer since capturing a record-equalling French Open in June.

Early exits in Montreal and Cincinnati again prompted questions over the Spaniard's recovery from a left-foot injury which had flared up at Wimbledon when he lost to Djokovic in the final.

Nadal's mood wasn't improved when he burned his fingers on his right hand in a Cincinnati restaurant.

Federer, meanwhile, is without a major since extending his record Grand Slam collection to 16 at the 2010 Australian Open.

With the great Swiss having celebrated his 30th birthday, and surrendered a two-set lead to lose in five to Jo-Wilfried Tsonga in the Wimbledon quarterfinals, his career obituaries are already being penned.

But Djokovic, Nadal and Federer, having won 28 of the last 31 Grand Slam crowns, are still comfortably the favourites for a final which falls on the emotional 10th anniversary of the 9/11 terror attacks on the U.S.

'I've played so many matches this year,' said Djokovic, this year's Australian Open and Wimbledon winner and the 2010 runner-up to Nadal at the U.S. Open.

'Considering the schedule, it's kind of normal to expect that at some stage you are exhausted.'

The Serb, whose only other defeat in 2011 was to Federer in the French Open semifinals, which ended a remarkable 41-match winning start to the year, insists that his shoulder problem won't hamper his Flushing Meadows campaign.