5. Juan Martin Del Potro
Though Del Potro is certainly a familiar name at the top of mens tennis, severe wrist injuries have hampered the Argentinians success over the last few years. The 24 year old has shown glimmers of his full potential having won the US open back in 2009. But since developing a wrist injury necessitating surgery Del Potro has had to work his way back into the top 10; he now looks like a potential candidate to cause an upset to the favourites (defending champion Andy Murray and world no.1 Novak Djokovic). Having climbed back up to 7th in the singles rankings Del Potro experienced a successful 2012, and in 2013 this 66 powerhouse has proved that he is back on top. He has beaten both David Ferrer and Novak Djokovic this year. To add to this, he pushed Djokovic all the way in the Wimbledon semi-final, eventually losing in the longest semi-final in the tournaments history (4 hours 43 mins). Though his form is less consistent and evidently more injury prone than his higher ranked opponents, the heavy hitter has all the weapons needed to disarm any player on the tour. Having won the Washington title and achieved a semi-final place in the Cincinnati (western and southern) open, his form in the hard court warm up tournaments ahead of the US open has been fantastic. Juan Martin Del Potro is my no.1 bet to challenge the favourites in the 2013 US open mens singles.