By now, we all know who the best tennis players in the world are.

Better known as the "Big Four," Roger Federer, Novak Djokovic, Andy Murray and Rafael Nadal have dominated the men's tennis scene for quite some time.

But, there just so happens to be a "Next Four" on the tour -- David Ferrer, Tomas Berdych, Jo-Wilfried Tsonga and Juan Martin del Potro.

The world No. 5 Ferrer is arguably the best "pound-for-pound" player on the circuit. At 5-foot-10 (and that's not accurate) and 159 pounds, the 30-year- old Spaniard somehow seems to keep getting better with age.

In his best season since turning pro 12 years ago, Ferrer has quietly amassed five titles in six finals this year and reached at least the quarterfinals at all four Grand Slam events, including brilliant semifinal runs at the U.S. and French Opens. He's actually reached the final four at three of the last five majors, which would qualify him as an elite player to be sure.

His four Grand Slam losses this year have come against the best -- Djokovic (Australian Open quarters), Nadal (French semis), Murray (Wimbledon QFs) and Djokovic (U.S. SFs) -- and there's certainly no shame in that.

And Ferrer, who recently led reigning champion Spain into a second straight Davis Cup final, will finish inside the year-end Top 10 for the fourth time in six years.

Vamos, David!

Meanwhile, the powerful 6-foot-5 Berdych just won last week's title in Stockholm, Sweden, where he overcame his fellow former Grand Slam runner-up Tsonga in a marquee indoor finale. The big Czech has appeared in four finals this year, going 2-2, including a runner-up finish at an ATP Masters event in Madrid, Spain.

The world No. 6 reached at least the quarterfinals at two of the four Slams this year, including a semifinal berth at the U.S. Open last month, and has reached at least the quarters at five of the last 11 majors, including a spot in a Wimbledon final in 2010. He also clinched the Czechs' Davis Cup semifinal victory over favored host Argentina last month.

Is an elusive Grand Slam title still in his future?

The 27-year-old strapping Frenchman that is Tsonga is a former Aussie Open finalist (lost to Djokovic in 2008) who reached a Wimbledon semifinal and French Open quarterfinal this year. He's 2-2 in his 2012 finals and will finish inside the year-end Top-10 for a third time in five years.

The seventh-ranked 6-foot-2 slugger has reached at least the quarters in eight of his last 16 Grand Slam tournaments, including the 2008 Aussie Open finale and a trio of semis.

Is Jo still on the go?

That brings up to del Potro.

The menacing 6-foot-6 Argentine star is fresh off his title in Vienna, Austria, last week and, when healthy, would have to be considered as the best guy just outside the "Big Four." Sorry, Ferrer.

"DelPo," who turned only 24 just last month, owns three titles in four finals this year and appeared in quarterfinals at three of the four majors in 2012, with only a Wimbledon QF escaping his grasp. He was also one of the three men's singles medalists at the Olympic Games, with his bronze hardware coming in just behind Murray's gold and Federer's silver at the All England Club, where DelPo upset Djokovic in the bronze-medal affair.

Before Murray captured the U.S. Open last month, DelPo had been the only player not named Federer, Nadal or Djokovic to capture a major title over the last seven-plus years. The Tandil, Argentina, native appeared well on his way to becoming a "Big Four" player himself before right wrist surgery curtailed his progress in 2010.

He was basically on-the-mend last year, but would now (hopefully) appear to be all the way back.

Note: Del Potro was sidelined for a month with a sore left wrist before returning in a big way with his title last week.

Will DelPo break through with a second major title next year? Only time will tell, but ya gotta think he definitely has a shot.