AP/Kathy Willens

It used to be that height was a disadvantage in tennis.

Tall players couldn't move as quickly as their shorter, more nimble counterparts. Low, flat returns would give them trouble, bouncing just below their knees causing back and knee issues as they stooped low to attempt a return.

But then the game changed. As racket head size increased and spin became a major offensive tactic, balls were bouncing higher, giving the player of average height trouble to make the return in their comfort zone. And athleticism and strength were incorporated into the training programs of major pros, making tennis athletes stronger and more athletic to meet the demands of the new high-intensity game.

This made way for the advantages that height does offer: big first serves, incredible reach at the net and for returning would-be aces, coupled with the strength required for all-court coverage.

The average height of player's in the top-16 of the ATP tour is 6'2", including John Isner (6'9"), Ivo Karlovic (6'10"), Marin Cilic (6'6"), Mark Philippoussis (6'5") and Mario Ancic (6'5").

And then there's the 6'6" Juan Martin del Portro. The 20-year-old from Argentina experienced a break-out summer in 2008, winning four consecutive events in the U.S. Open Series and making his way into the tennis spotlight. Fast forward to the 2009 U.S. Open, where del Potro not only won the final in a five-set thriller, but beat both Rafael Nadal and Roger Federer in the process.

And it's not just his height and his 134 m.p.h. serve that makes him such a formidable opponent. His on-court movement is surprisingly quick for his size, and his greatest weapon, his blistering cross-court forehand, kept Federer scrambling during the Open final and was eventually the shot that spelled his downfall.

So in addtion to the gifts a player needs to succed in pro tennis -- exceptional athletic ability, hand-eye coordination, and a solid work ethic -- you can add to the list  towering height.

Unfortunately, this latest addition isn't something that can be learned.