5. John Rocker
Career Years: 1998-2003
Career Lowlight: His 1999 Sports Illustrated interview.
While there is no scientific way to measure it, Rocker might just be the biggest asshole ever to play a major professional sport. The 'roided up relief pitcher's December 1999 Sports Illustrated profile remains the standard for ignorant, horrible comments both in terms of their level of vitriol and sheer volume. Probably the only good thing he did was serve as the inspiration for Kenny Powers of HBO's Eastbound and Down. In a bit of karmic payback, Rocker's career completely fell apart after less than three years as the Braves' closer, and by 2004 he was out of Major League Baseball entirely.