20. Ryan Mattheus (2013)
Mattheus joined the ranks of MLB stars who punched a hard object and paid the price. The Nationals’ right-hander endured a tough game against San Diego. His reaction was to go back inside and punch his locker. But this simply broke his hand and put him out of action. Later, Mattheus opened up on his ridiculous injury and explained how it affected him psychologically (via SBNation).

After describing it as a ‘boneheaded move,’ Mattheus revealed that he was disappointed in himself. “I had to sit around for two months and watch my teammates try to get back in that thing, you know,” he told reporters. And that’s tough to swallow walking in that clubhouse every day and seeing guys working hard on winning ballgames and I was working hard trying to fix something that I did that wasn’t very smart.”