Here's a fun fact: Pitching does incredible physical harm to pitchers. The unnatural motion takes a significant toll on the body, often doing lasting damage to the elbow, shoulder, back and/or knee. So the starting pitcher position is baseball's equivalent to the NFL running back. Because the men who do it may be capable of dominating the league in their first season or two. But by then they're highly prone to various likely injuries. And if physical ailments catch them, they sometimes disappear from the mound forever. Just ask the likes of Mark Prior, Dwight Gooden, Mark Fidrych and Sandy Koufax. You'll find all of them on our list of the greatest MLB careers derailed by injury.