Juan Martin del Potro. Many forget to mention del Potro when speaking of top contenders, but his potential on the hard court is undeniable. Del Potro won 23 straight matches last summer, capturing four tournament victories in a row leading straight up to the 2008 US Open, besting any teenager in tennis history except for Rafael Nadal.

Del Potro reached the quarterfinals at least year’s open, but was stopped short by Andy Murray in a four set nailbiter. Murray went on to advance to the finals. This is all an indication that an improving Del Potro can’t be overlooked at this year’s tournament.

Andy Roddick: Andy Roddick is realistically the only American hopeful at grand slam events, and has remained that way for quite some time. For a long time, Roddick often occupied the 5-8 seeds, although such a high seeding was virtually meaningless given the dominance of top 3 players Roger Federer, Rafael Nadal, and Novak Djokovic. Federer has since experienced some shakiness, Nadal has struggled with injury, and Djokovic’s mental game has affected his performance, thus opening the door for players like Roddick to make a measurable impact.

Roddick won his only grand slam at the US Open in 2003, but this seems like ages ago in the tennis world. Still, a newly invigorated Roddick (with an emphasis on fitness) made the Wimbledon final, and played an incredible match against Roger Federer, nearly defeating him. Between Roddick’s momentum, his huge serve, and the spirit of the home crowd behind him, Andy Roddick’s chances can’t be discounted at the 2009 US Open.

Andy Murray. Murray seems to be improving his game with each year, and 2009 has been no exception. Stealing the #3 spot from Novak Djokovic, Andy Murray has the poise and skill set to win a grand slam. He went his furthest ever in a slam in 2008 at the US Open, losing to Roger Federer in the final, but a young 22-year-old Murray could easily show us that last year was no fluke.

Rafael Nadal: Very arguably the world’s best current tennis player when healthy, Rafael Nadal has dominated the clay courts, defeated the king of Wimbledon (Roger Federer) at the 2008 final, and did so once again at the Australian Open final earlier this year, giving Nadal grand slam wins on all three surfaces. Since Nadal was the most recent hard court grand slam winner, there’s absolutely no reason he can’t win a US Open. However, two things stand in Nadal’s way: injuries, and a history of struggles at the US Open. Rafael Nadal was forced into sitting out Wimbledon in 2009, and one has to wonder if his loss at the French to Robyn Soderling had anything to do with his recurring knee injury.

Nadal is rested and plans to return for the hard court season, but the extent to which he can make an impact remains unknown, as his knees are still untested since his injury. Hard courts are no friend to ailing knees, as the surface puts more strain on the body than any other does. Additionally, Nadal has never made it past the US Open semifinals, losing to players like James Blake (2005, 3rd round), Mikhail Youzhny (2006, quarterfinals), David Ferrer (2007, fourth round), and Andy Murray (2008, semifinals). Nadal has some major hurdles to overcome this year, but never backs down from a challenge.

Roger Federer: Ah, the king. The newly anointed king of tennis won his record-breaking 15th grand slam at Wimbledon in 2009. With some help from an injured Rafael Nadal, perhaps the only player who arguably has Federer’s number, the road was easier for Federer…but still an extremely challenging one given Federer’s struggles in 2008, an increasingly competitive field, and his age of 28. Despite all this, what is most impressive is that Federer has won each of the last five US Opens since Roddick won in 2003. To win five straight Grand Slams positions Federer as the obvious favorite at this year’s US Open. For his sake, let’s just hope he doesn’t meet Nadal in the finals.

This sums up my predictions for this year’s tournament. Can’t wait for it to begin!