Hi all...first time poster here.
2 other interesting cases of players whose careers succumbed to mental barriers they could never overcome were Mackey Sasser and Kevin Saucier.
Sasser was probably the more notorious of the 2 because, as a catcher for the Mets, he developed an inability to throw the ball back to the pitcher. he'd end up sailing the ball into the outfield and would even throw little dribblers back to the pitcher to try to get it back to him. He eventually tried converting to the outfield, but his career was basically done at that point.
Saucier was an interesting case because he was an "on the rise" reliever with Detroit in the early 80's who suddenly lost control of his fastball. He developed such an overwhelming fear that he would hurt someone that he just walked away from the game.
The power of the mind