Juan Martín del Potro (1988-) - 6'6" Argentine Tennis Great, and Winner of the 2009 U.S. Open

[DonRocks]

I'm not sure this merits its own topic, but I'd like to nominate Juan Martín del Potro as "Most Underrated Player in History" - he's the only "non-Big Four" player to win a Grand Slam between the 2005 French Open and the 2013 U.S. Open (that's 35 tournaments) - in the 2009 U.S. Open, he beat Nadal in the semifinals and Federer in the finals.

del Potro is *great*, but nobody really knows him because he's been overshadowed by a handful of space aliens (plus he's been forced to battle injuries).

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And as long as I'm off-topic, I'd like to nominate Jack Sock for "Sportsman of the Year" for this amazing display where he *advised an absolutely dumbfounded Lleyton Hewitt to challenge a serve that he knew was in*! 

Almost as if to prove the existence of karma, Sock just won an Olympic gold medal in mixed doubles.