Though there's been great parity in recent women's Grand Slam tournaments, with seven winners in the last seven Slams, the men's side has been completely dominated by the Big Three of Roger Federer, Rafael Nadal and Novak Djokovic.
This year's U.S. Open is the first Grand Slam event in a while that offers a real opportunity for a sleeper to win in both the men's and women's tournaments.
On the men's side, Nadal's withdrawal from the tournament due to injury leaves one less Goliath to defeat. Though Federer is in the midst of a late-career resurgence, it's been four years since he's won at Flushing Meadows, and Andy Murray showed at the Olympics that Federer is not invincible.
Any sleeper on the gentleman's side will still have to top defending champion Djokovic, but he does not yet have quite the aura of invincibility that surrounds Federer and Nadal.
On the women's side, Serena Williams's recent return to dominance has left many of her opponents nervous, but the U.S. Open is the venue that rattles Williams the most. She has had emotional outbursts at the last two Opens she played in, and she told the New York Times, according to Paul Newman, that she thinks something will likely go wrong again at this year's Open.
While Williams' total of three singles titles at the U.S. Open is an amazing feat, she's only won the major once in the past decade.
These factors are just enough to give Williams' opponents hope that they can defeat her at Flushing Meadows and continue the era of parity in the women's game.
Here is a look at five sleepers, two on the men's side and three on the women's side, who have what it takes to surprise the tennis world with deep runs at this year's U.S. Open.
The 28-year-old Philipp Kohlscreiber has been one of the better singles players on the men's tour since winning his first ATP event in April 2007, at the BMW Open in Munich.
He has won three more ATP events since then, most recently at this May's BMW Open and reached three more finals. Just a month ago, he reached the final at the Austrian Open Kitzbuhel, where he lost in three sets to Robin Haase.
Though he's found success on the tour, Kohlschreiber has mostly been a nonfactor at the majors. Between his first major in 2003 and the end of 2011, Kohlschreiber failed to reach the quarterfinal round at any major, though he reached the fourth round three times.
This year, Kohlschreiber has started to look like he just might have a major victory in him. He reached the fourth round at the Australian Open, and after an early exit in the second round of the French Open, he reached the quarterfinal round at Wimbledon, where he lost in a spirited match against Jo-Wilfried Tsonga.
A win at the U.S. Open by Kohlschreiber would be a huge surprise. Though he was once touted for great things, he has settled into the mid-teen rankings, a threat to win minor events but a perpetual also-ran at more prestigious tournaments.
But, he has been playing strong lately, and after a career-best performance at Wimbledon, he will be focused on improving even further in Flushing Meadows.
After winning three ATP events in 2008 and 2009 and then finishing 2009 with a quarterfinal appearance at Wimbledon at 20 years old, Marin Cilic was tapped as one of the most promising young prospects in tennis. He reached the semifinal round at the following year's Australian Open, but lost to Andy Roddick in five sets.
Since then, Cilic has made much less of an impact on the majors, failing to advance past the fourth round at a Grand Slam event. Yet, he has remained a regular contender at ATP tour events.
Since the start of 2010, he has won five ATP events and was the runner-up at five more. This year, he lost to Philipp Kohlschreiber in the final of the BMW Open, and then, won the Queen's Club Championships in June and the Croatia Open in July.
Cilic has played well against many of the top players in the game and has come out on top against players such as Rafael Nadal, Andy Roddick, John Isner, Andy Murray and Jo-Wilfried Tsonga. Novak Djokovic and Roger Federer have had little problem beating Cilic, however, posting records of 6-0 and 3-0 against him, respectively.
It is hard to believe that Cilic is only 23 years old, and as he continues to add depth to his game, he becomes more of a threat to win a Slam. No one in his age bracket has yet established himself as a successor to the Big Three, and if Cilic continues to develop as he has, he will have opportunities to win a few majors.
Li Na is peaking at the right time in her effort to win the 2012 U.S. Open. Li, who won the 2011 French Open, finished 2011 with a second-round exit at Wimbledon and a first-round loss at the U.S. Open.
She started 2012 strong with fourth-round runs at the Australian and French Opens, and though she didn't make much of an impact at Wimbledon, she has found success at non-major ATP events.
Li reached the finals at three ATP events in 2012, losing to Victoria Azarenka, Maria Sharapova and Petra Kvitova, with the last loss coming just two weeks ago at the Canadian Open. She rebounded from her final loss to defeat Angelique Kerber in three sets at the prestigious Cincinnati Masters.
Li has played well at the U.S. Open in the past, reaching a career-best quarterfinal at the 2009 Open, where she was easily beaten by Kim Clijsters.
Li has shown that she has what it takes to win a major, and if she continues to play like she has the past few weeks, there is no one she cannot beat.
Kim Clijsters has announced that she will retire after her run at the 2012 U.S. Open. Though the Belgian star hasn't won a tournament since the 2011 Australian Open, she has still played remarkably well despite battling ankle injuries.
Of Clijsters' four Grand Slam victories in her career, three came at the U.S. Open, and she has never finished short of the quarterfinals in the tournament. She missed last year's tournament, but won in both 2009 and 2010.
This year, Clijsters reached the semifinal at the 2012 Australian Open, missed the French Open and reached the fourth round at Wimbledon, all while battling injuries.
If Clijsters is completely healthy, the former top-ranked player has the necessary experience at Flushing Meadows to make a deep run at the tournament. Lingering pain in her ankle would hamper her effort, but it still might not stop her.
Anastasia Pavlyuchenkova has reached the No. 20 ranking nearly entirely as a result of her strength on hard courts. Each of Pavlyuchenkova's four WTA finals, including three victories, came on hard courts, including a loss in the final at the Citi Open in Washington, D.C., earlier this month.
Pavlyuchenkova reached the fourth round of the 2010 U.S. Open, her best Grand Slam performance at that time and then reached the quarterfinal of the 2011 tournament, where she lost to Serena Williams 5-7, 1-6.
Pavlyuchenkova is only 21 years old, and she has taken a big step forward over the past two years. In a major with only a few favorites, Pavlyuchenkova could slip into the top of the tournament for the first time in her major career.