Novak Djokovic: Shoulder Injury Latest Reason He's in Trouble at 2011 US Open

Novak Djokovic retired due to an apparent shoulder injury in the second set of the Western and Southern Open final. With the 2011 U.S Open just a week away, it is uncertain whether he will be able to recover in time.

Djokovic said that his shoulder had been bothering him well before he pulled out of the tournament in Cincinnati, Ohio. Despite whatever injuries he may have been previously dealing with, he has been on a tear in 2011. Djokovic's loss in the Western and Southern Open was just his second of the year, putting him at 57-2 in 2011.

He has been unstoppable this year, only losing one full match to Roger Federer in the French Open.

"What he's done this year is like Xbox," said Andy Roddick of Djokovic, as reported from USA Today. Roddick's comment obviously shows that not only the fans and media have been impressed with Djokovic's run.

What does this mean for the U.S. Open?

Djokovic took the No. 1 world ranking from Rafael Nadal after he defeated him at Wimbledon earlier this summer. Djokovic would have been the clear favorite to win the last Grand Slam of the year, but people are already beginning to speculate who the new front runner will be.

Rafael Nadal is the reigning champion at Queens, New York. He beat Djokovic in four sets to capture the 2010 U.S. Open title, his first ever at Flushing Meadows. However, Nadal has been slumping lately, and is also dealing with a burn injury to his hand. 

Roger Federer won five U.S. Open titles consecutively from 2004-2008. Yet Federer, now 30, is losing more often these days. 

There are some tennis fans that are ready to give the trophy to Andy Murray. Murray has been predicted to win a major for quite some time now, but he has yet to make it happen. He has reached one U.S. Open final, 2008, where he was easily put away by Federer in three sets.

Murray took a while to recover after losing the Australian Open earlier this year. After he was beaten in straight sets by Djokovic in the finals, he lost three straight tournaments in the first match.

Djokovic has no doubt played through pain before, but no one knows how much pain he is dealing with right now, or how far he is willing to play with this injury. Before he retired against Murray in Cincinnati, Djokovic was serving in the double digits, and was unable to put anything on his forehand.

The Djoker apologized to his fans via Twitter after he retired, saying he hopes and believes everything will be ready for the U.S. Open. He has a week to recover and prepare, but if he isn't at full strength look for the other top seeds to take advantage.