Herschel Walker is an NFL legend. Though he never played on a championship team, he is fifth all-time on the NFL's rushing list. He is first overall in the NFL for all-purpose yards. He's the only player in the league's history to earn 4,000 yards three different ways: rushing, receiving, and kick-off returns. In short, he's a Hall of Famer - who decided to take some professional MMA fights in his late 40s. Claiming to be in better shape in his forties than his twenties (and frankly doing his best to back it up), Walker joined the Strikeforce promotion in 2009, after announcing his intentions to fight in 2008. Training with American Kickboxing Academy (who would produce UFC champions Cain Velasquez and Danial Cormier, he took his first fight, at heavyweight, in 2010, defeating Greg Nagy, and his second a year later, where he again won against Scott Carson. Both fights were TKO victories, however when the UFC purchased Strikeforce, they opted not to use Walker.