Rafael Nadal is one of the favorites to defend his title at Flushing Meadows in a couple of weeks' time. But, other than world No. 1 Novak Djokovic, Nadal can expect quite a few tough challengers vying for his crown.
The world No. 2 and French Open champion has already been shocked twice since his record-equaling feat at Roland Garros two weeks back—once by an acrobatic Frenchman and once by a never-heard-of-before Croatian.
While Nadal and Djokovic have stolen the limelight over the last year or so, they have overshadowed many good players in the draw who are capable of causing an upset or two.
Here's a list of the 10 most underrated players going into the U.S. Open.
10th ranked Nicolas Almagro has enjoyed a good season so far in which he reached the fourth round of the Australian Open and the third round of Wimbledon.
The Spaniard's preferred playing surface is clay, but he's currently having a good hard court season.
Almagro was impressive in the Rogers Cup, where he trampled over Sergiy Stakhovsky 6-2, 7-6 and overwhelmed Richard Gasquet 7-6, 6-3. He would lose to Jo-Wilfried Tsonga 7-6 (3), 4-6, 6-1 in the quarterfinals.
Almagro is an aggressive baseline player and has powerful groundstrokes. He also has a very swift service motion which produces a lot of speed.
With a little more dedication, Almagro could just surprise everyone at the U.S. Open.
Janko Tipsarević has been overshadowed by his more illustrious compatriot, Novak Djokovic, throughout his career.
But the 27-year-old is a very enjoyable player to watch, with his flashy shades et al.
2011 has been a sort of a breakthrough season for Tipsarević.
The Serbian, who reached the semifinals at Montreal, recently reached a career-high ranking of 20th in the world. He has a decent 34-17 win-loss record this season.
Tipsarević beat Alejandro Falla, Fernando Verdasco, Ivan Dodig and Tomas Berdych en-route to the semifinal, where he lost to Mardy Fish. This was his first appearance in the semis of an ATP Masters 1000 series.
Tipsarević, on a good day, can prove to be a tough nut to crack. He's never gotten past the fourth round of a Grand Slam, but recent performances will give him confidence for the rest of the hard court season.
Known as the "Miracle of Medjugorje," Marin Čilić has a reputation of being a giant-killer.
The 22-year-old Croatian has beaten players such as Rafael Nadal, Andy Roddick and most recently, Juan Martin del Potro.
Čilić's game is built on an outstanding junior career where he was ranked second in the world in 2005. He was also coached by fellow countryman Goran Ivanišević for a brief period.
Čilić has a great backhand and is able to make his opponent run around the court and dictate points.
Čilić has already beaten Nadal before and, given the Spaniard's erratic form, could cause another upset in the US Open.
Čilić's best performance at a Grand Slam is a semifinal appearance at the 2010 Australian Open.
With a little more hard work and luck, the Croatian might just go the distance soon.
Gael Monfils, ranked eighth in the world, has had some good results this summer.
The Frenchman has a 25-10 record this season but hasn't won a title so far. He got close in Washington, D.C., but was edged in the final by Radek Stepanek. He also reached the quarterfinals of the Rogers Cup, where he lost to world No. 1 Novak Djokovic.
Monfils, who plays a counter-punching style of tennis, has two of his three career title wins on hard courts. He has even beaten Nadal once on the surface.
Monfils is often compared to the Spaniard due to his athleticism. His form in the hard court season has been good so far and he would be aiming for a strong U.S. Open performance.
Tomáš Berdych had a strong first round of hard court tournaments earlier this year when he reached the quarterfinals of the Australian Open, Rotterdam and Marseille, and the semifinals of Chennai and Dubai.
Berdych played his first tournament in the second round at the Rogers Cup, where he beat players such as Alexandr Dolgopolov and Ivo Karlovic.
Although he hasn't been able to reproduce the form that led him to the Wimbledon final last year, he's looking strong and focused.
Berdych was beaten by Nadal in that Wimbledon final and has a 3-10 record against the Spaniard. The Czech would sure be looking to improve that record.
David Ferrer is one of the best returners in the game and also one of the most underrated players in the game.
A consistent Top 10 player for the last few months, Ferrer has been overshadowed by his more illustrious compatriot, Rafael Nadal.
Ferrer is known to be a clay court specialist, although his best performances at a Grand Slam have been semifinal appearances at the Australian and U.S. Opens.
In the 2011 Australian Open, seventh-seeded Ferrer beat top seed Rafael Nadal in straight sets in one of the biggest victories of his career.
After a hectic summer of tennis, Ferrer withdrew from the Rogers Cup due to an injury to his left hand. But he's back on the tour for the Cincinnati Masters in preparation for the U.S. Open.
Expect the Spaniard to put in a strong challenge at both tournaments.
Mardy Fish, who entered the top 10 for the first time in April this year, is currently enjoying the strongest hard court season of his career.
After winning the Atlanta ATP event, the 29-year-old American reached the finals of the Farmers Classic and the Rogers Cup—both of which he lost.
His performance in the hard court season has shot up his ranking to No. 7 and he seems to be gaining in confidence as the matches go by.
His counter-punching style and superb court coverage might just help him spring a couple more surprises at the U.S. Open.
Juan Martin del Potro isn't having the best of hard court seasons, but you can never count the towering Argentine out.
After winning the 2009 U.S. Open, del Potro spent most of last season on the sidelines due to a wrist injury. He has been fighting his way back up the rankings this season.
Del Potro took a set off Novak Djokovic and Rafael Nadal at the French Open and Wimbledon, respectively. He will always remain a major threat wherever he plays.
Del Potro loves playing at Flushing Meadows and couldn't defend his title last year due to injury. He'll be gunning to do it this year.
Jo-Wilfried Tsonga loves playing on hard courts. Some of the best results of his career have come on the surface.
The Frenchman is an unpredictable player. You can never tell when he's going to pulverize you with his groundstrokes or when he's going to surrender meekly.
Tsonga has already beaten Rafael Nadal once and Roger Federer twice this year. On the other hand, he retired halfway through his Rogers Cup semifinal match against Novak Djokovic and lost in the second round of the Cincinnati Masters to Alex Bogomolov Jr.
But the Frenchman is known to be a big-game player and is famous for causing upsets. Regardless of his pre-tournament form, Tsonga will be a valid threat to Rafael Nadal's crown at the U.S. Open.
Roger Federer is not only the shock addition to this list, but also tops it.
After a mediocre season so far in which he has failed to win any major, the Swiss Maestro has come under a lot of criticism.
There have been plenty of calls for the 30-year-old to hang up his boots.
Although he is ranked No. 3 in the world, Federer will, at best, be given an outside chance to win the tournament he has won a record five times.
Federer has been overshadowed this season by the two men ranked above him—Novak Djokovic and Rafael Nadal—and not many believe that he can beat them.
But all I've learnt from watching Federer over the years is that you can write him off at your own peril!