When it comes to Grand Slam events, the U.S. Open is notorious for being the most unpredictable of all. Underdogs shine under the bright lights of New York City, and the Open is the only Grand Slam since the 2005 Australian Open that has seen someone other than the big four win the title.
The question is, which of the top contenders in 2013 have the best chance of dethroning the three remaining members of the big four?
Since 2008, five different male players have won the U.S. Open championship. It's the only Grand Slam that can stake that claim, as either Novak Djokovic, Roger Federer, Andy Murray or Rafael Nadal have won at least two titles in that time at other major events.
If that's not enough, the last time a player outside of the big four won a Grand Slam was the 2009 U.S. Open, when Juan Martin del Potro shocked the world. In 2013, there is a legitimate possibility for history to repeat itself as an underdog will look to rise and upset the biggest names in tennis.
The question is, who might that be?
Tomas Berdych, Czech Republic
ATP Rank: 5
Best U.S. Open Result: Semifinals (2012)
Few players have been performing as well as Tomas Berdych of the Czech Republic, regardless of what their ranking may be. Berdych hasn't dropped a single set at the U.S. Open and dismantled No. 31 Julien Benneteau 6-0, 6-3, 6-2 in the third round.
Should he get by Stanislas Wawrinka, Berdych will have a legitimate shot at the title.
Berdych is one of the closest players in the world to the big four, but he has struggled to maintain focus in critical matches. Even still, Berdych has three quarterfinals appearances at the Australian Open, semifinals berths at the French Open and U.S. Open and a finals appearance at Wimbledon.
At the 2013 U.S. Open, it certainly seems as if the 6'5" slugger has found his head.
Getting past Wawrinka will be tough, and if he does, a potential match against Andy Murray looms. With that being said, Berdych has the ability and power to upset both Murray and Novak Djokovic, which makes him an intriguing contender to watch.
It certainly won't be easy, but when is it ever at the U.S. Open?
David Ferrer, Spain
ATP Rank: 4
Best U.S. Open Result: Semifinals (2007, 2012)
Outside of the big four, David Ferrer is the most consistent player in the world. Even as he's struggled in the minor ATP Tour tournaments, Ferrer is the No. 4 player in the world for a reason.
Ferrer has reached the quarterfinals in eight consecutive Grand Slam events, including the 2013 U.S. Open.
His ability to crack the final eight hasn't delivered a major just yet, but even at 31, he's still performing at a high level. Ferrer has no trouble competing with the big four and is one of the most well-conditioned players in the world.
Already in the quarterfinals, it'll take just three more wins to become the U.S. Open champion, albeit three difficult victories.
Ferrer outlasted No. 18 Janko Tipsarevic in the fourth round, winning 7-6 (7-2), 3-6, 7-5, 7-6 (7-3). This victory was the definition of Ferrer's contender status, as he's physically and mentally tough enough to overcome any challenge, giving every opponent trouble with his ability to return all shots sent his way.
Keep in mind, Ferrer was a finalist at the French Open, semifinalist at the Australian Open and quarterfinalist at Wimbledon in 2013. If anyone can get over the hump and break through, it's him.
Richard Gasquet, France
ATP Rank: 9
Best U.S. Open Result: Quarterfinals (2013)
Richard Gasquet has been on the cusp of greatness for years on hand, reaching the fourth round in 17 Grand Slam events. That includes seven of his past eight and 10 of his past 13 appearances, but he's failed to reach the quarterfinals since the 2007 Wimbledon.
Gasquet had reached the fourth round in four separate U.S. Open appearances before this year, but conditioning and mental focus always got in his way. During his fourth-round match against No. 10 Milos Raonic, however, Gasquet made dramatic strides and finally shattered the glass ceiling.
With Raonic in control and dominating with his serve, Gasquet fought back from one set down to win a fourth-set tiebreaker and a tight fifth set. In the end, Gasquet took home a 6-7 (4-7), 7-6 (7-4), 2-6, 7-6 (11-9), 7-5 win.
Up next is a game Ferrer, but don't think Gasquet can't break through.
If Gasquet is able to get past Ferrer, anything is possible for the Frenchman, whose upside has been revered for the better part of a decade. Now in the prime of his career, Gasquet is a top-10 player and has now cured the woes that plagued him in years past.
He's a long shot, but don't think that makes him any less legitimate.
Stanislas Wawrinka, Switzerland
ATP Rank: 10
Best U.S. Open Result: Quarterfinals (2010)
When it comes to Stanislas Wawrinka's success at 2013 Grand Slam events, the only word to describe his play is "finally." He reached the fourth round at the Australian Open and quarterfinals at the French Open. He currently is playing in the fourth at the U.S. Open as well.
With a win over Berdych, Wawrinka would make his second career U.S. Open quarterfinals appearance.
Wawrinka has been playing some of the best tennis of his career in 2013, winning the Portugal Open and making three other finals appearances. During the U.S. Open, he's defeated quality opponents in Raden Stepanek, Ivo Karlovic and Marcos Baghdatis.
Unranked or not, all three of those players are respected and more than capable of pulling off upsets on highly ranked players.
Wawrinka has always been hyped as one of the best players to not win a major, but he's been unable to live up to the talk. By defeating Berdych, Wawrinka would effectively put himself into title contention and set up a match against Andy Murray that could alter his legacy.
No one's ever questioned Wawrinka's talent, and it'd feel strange without a Swiss star in the title picture—even if it isn't Roger Federer.