But this can happen for any number of reasons. He may have some type of learning dyslexia for instance, its really hard to spot. Maybe he is not the smartest guy and just isn't up to understanding the more complex stuff that BB expects everybody to get.
You don't just lose skill, if you have it in you its there until you get old, slow down or whatever. You can lose your hunger and your are done or have an attitude problem or simply be lazy. A change of scenery can give you back that element that you were missing.
Look at Mike Williams in Seattle at the minute, former first round pick who never did anything since he came out of college. He didn't even try out for a team last year and he is looking like a starter for the Seahawks this season. Everybody thought Moss was done when he came here, Corey Dillon too.