Mar 12, 2009 2:00 PM EST

Many believed Mark Prior's delivery represented perfect mechanics, but he actually was putting a great deal of stress on his shoulder with each pitch.

He hasn't thrown a pitch in the big leagues for three years.

?I tried to tell people: ?My mechanics are not perfect,? ? Prior said. ?I was still working on things all the time. No one ever seemed to get that. People liked it because it didn?t look like I was trying. It wasn?t until the injuries. Then people started saying because I do this, that happens.?

He put off surgery until April 2007, when doctors operated on a torn labrum and split shoulder capsule.

?My arm hurt all the time,? Prior said. ?Nobody could tell me what?s going on. I could see my performance wasn?t the same. You?re trying to compete with inadequate stuff, and you get down on yourself, and you get bitter and negative. Having the surgery was almost a relief. ?

Via Yahoo!