Grigor Dimitrov could make a Grand Slam run this year.
Only four other players, other than those four, have won a slam since Federer won his first in 2003.
As Federer enters the waning stages of his career, now is the best chance for a fresh face to break the run the Big Four have on Grand Slams.
Will it be one of the young guns like Grigor Dimitrov or Milos Raonic? Or perhaps a hungry, slam-less veteran like Jo-Wilfried Tsonga or Tomas Berydch?
Winning a Grand Slam takes skills, persistence, mental toughness and sometimes a little luck.
Sometimes it takes a few failures in finals before the big breakthrough.
Rarely does a player burst onto the scene like then-unseeded 17-year-old Boris Becker and grab a Slam. If it happens again, fans will be stunned and delighted. However, most likely, the players who have the best chance of pushing past the Big Four are in the mix right now.
Juan Martin Del Potro
Juan Martin del Potro already won a Grand Slam; he defeated Federer to capture the 2009 U.S. Open.
He also nearly defeated Federer at the 2012 Olympics.
Whether del Potro wins another Slam depends on if he decides to show up.
Sometimes del Potro becomes deflated during matches, almost lazy. He was the first Top-10 player bounced from the 2013 Australian Open.
When healthy, hungry and focused, del Potro is as good as it gets on hard courts.
Unlikely that we will see a teenage unknown like Becker win a Slam anytime soon.
Slam winners often emerge after a steady climb toward the top, and they usually pull off a few big upsets along the way.
Raonic is on that steady climb. His fourth-round loss to Federer at the 2013 Australian Open gave him invaluable experience about prime-time matches against big opponents.
This year, he also led Canada to its first Davis Cup semifinals with two wins against Italy.
Richard Gasquet at 2013 Sony Open
Richard Gasquet is quietly putting together a solid year on the tour. The 26-year-old Frenchman is ranked No. 9 and could be a sleeper going into the French Open.
When he was 21 he was one of only three active players to win titles on all three surfaces.
Gasquet has consistently gone deep into tournaments this year. He reached the semifinals in Miami, where he lost to winner Andy Murray. He also reached the quarterfinals in Monte Carlo.
Grigor Dimitrov, aka Baby Fed
With a nickname like Baby Federer, how can you not win at least one Grand Slam?
Dimitrov has garnered respect from Nadal, who found it hard to believe the youngster wasn't ranked higher. After their match in Monte Carlo, Nadal told the ATP that he expects Dimitrov to be a Top-10 player someday.
Federer won his first Grand Slam at age 21. Could Baby Federer do the same?
If Stanislas Wawrinka is going to win a Slam it will probably happen this year.
Wawrinka has all the shots, the talent. But he's also had the tough task of playing in the shadows of fellow countryman Roger Federer.
Perhaps a coincidence, but Wawrinka's game is on the rise as Federer's appears on the decline.
If "Stan the Man" keeps this up, we may see another Swiss sensation holding a Grand Slam trophy.
When you talk about No. 8 Jo-Wilfried Tsonga and Grand Slams, the question isn't when, but why?
Why hasn't Tsonga won one already?
The answer lies between his ears.
Tsonga has all the size, the shots and talent needed to win a Grand Slam. What he lacks is patience and poise. How many times have we watched him put together a near flawless set only to later melt down mentally.
Time is running out on the Frenchman. But if Tsonga can keep it together for just a few hours, he can beat anybody, anywhere.
Might as well be in a Grand Slam final.