In 2006, Pro Baseball Relief Pitcher Joel Zumaya had to sit out three games of the American League Championship Series in October of that year. This was due to an injury he got while playing Guitar Hero on the Playstation 2. He suffered inflammation in his right (throwing) wrist and forearm from playing the game. His team asked him to stop playing the game, and he pitched pain-free in the World Series.
"When Zumaya went to the Tigers training staff about his injury, they noticed his pain was more consistent with a guitar player than a baseball pitcher"
After quitting Guitar Hero, Zumaya could throw the ball more than 100 mph, was 6-3 with a 1.94 ERA in 2006.
His injury was mentioned in the credits for the Xbox 360 version of Guitar Hero II:
"No pitchers were harmed in the making of this game. Except for one. Joel Zumaya. He had it coming."
Sources:
http://nbcsports.msnbc.com/id/16212095/
http://en.wikipedia.org/wiki/Joel_Zumaya