Due to the extended absence of Rafael Nadal, Juan Martin del Potro has a real possibility to break into the top four.
Del Potro is entering the new season ranked seventh, although he is a mere 200 points behind Tomas Berdych who is ranked sixth. One distinction that separates del Potro from Berdych and David Ferrer is the Argentine has won a Grand Slam title.
At the 2009 U.S Open, del Potro became the first player to beat both Rafael Nadal and Roger Federer in the same Grand Slam.
Delpo upset Federer in the 2009 U.S Open Final, handing Federer his first loss in New York since 2003. Even more outstanding than the victory itself was the manner in which del Potro triumphed.
Down two sets to one, many expected del Potro to succumb to Federer, who is widely known as a lethal closer. Instead, Delpo overpowered Federer and announced his emergence as a star.
Del Potro also gained invaluable big match experience, which will ensure he won't be overwhelmed on the biggest stages in tennis.
With a booming serve and overpowering forehand, del Potro has the game to beat anyone in the world on any given day. Not surprisingly, del Potro is at his best when he is being aggressive and dictating play with his forehand.
However, the Argentine has struggled with consistency since returning to the tour after missing the majority of the 2010 season due to a wrist injury.
After winning two tournaments last fall and two wins over Federer, Delpo appears to have his confidence back. If his newfound confidence translates into more intimidating on-court performances, then del Potro will back-up his 2009 U.S Open title with authority.
The top four has been solidified for so long due to the greatness of Federer, Nadal, Novak Djokovic and Andy Murray. However, with Nadal missing time due to a knee ailment and Federer cutting back on the amount of tournaments he enters, an opportunity to move up the rankings is now plausible.
If anyone is going to make an ascent into the top four this season, it will be del Potro. In order to move up the rankings, Delpo will need to avoid injury while posting consistent results against the players ranked below him.
Del Potro is currently 2,180 points behind Nadal, who is currently ranked in fourth. However, Nadal has withdrawn from the Australian Open and will lose the 1,200 points he received for reaching last year's final.
In 2012, Delpo reached the quarterfinals of the Aussie Open. With a deeper run at this year's event, del Potro could conceivably jump Nadal in the rankings before the Spaniard returns from injury.
Sure, del Potro will also need to jump Berdych and Ferrer to break into the top four, but he is more dangerous than those two players are when in peak form. As long as he is playing his game well, del Potro will be able to usurp them in the rankings.
Del Potro became one of the few players who could give Federer and Nadal trouble during that duo's heyday, but he now faces a new challenge.
While Federer and Nadal are still relevant and dangerous, Novak Djokovic and Andy Murray are younger and will be atop the rankings for the foreseeable future. The success of del Potro will be dependent on his ability to beat Djokovic and Murray, something he has struggled with up to this point, as he is 3-12 combined against the duo.
He will need to overcome Murray at the Australian Open to better the result he posted last year, as del Potro is in Murray's quarter. Although overcoming Murray/Djokovic will be tricky, Delpo has the firepower and serve to solve the puzzle.