I would argue that bad coaching can also get inside of a young player's head to the extent that "it" has a hard time overcoming poor instruction. I'm not suggesting that EJ definitely has "it," but there were a few times in the first season when it seemed that a game was on the line and he stopped thinking, and was able to play a more instinctual game. The Pats* game in his first start comes to mind. OT in the Atlanta game comes to mind. There were others.
It was mentioned upthread by KD about Rex letting Geno play to see what he had. Unfortunately for Rex, Geno is a brick, and he proved that he is a turnover machine that has a hard time thinking about the reprecussions of blindly pulling the trigger, but I would have loved to see EJ in a similar situation where taking care of the ball was not the first, second, third, and fourth priority that appeared to be drilled into his head.
IMO, Marrone completely missed the point of taking chances on offense when you have a defense that can bail you out if you turn the ball over. He should have tried harder to develop a young QB with a defense like that to fall back on, but I suspect in the back of his mind he had one foot out the door the second the prospect of the ownership change entered the picture. Unfortunately, his self-serving approach leaves the franchise in the same spot it was at the beginning of last season, with a playoff caliber roster that is now 1 year older and a big unanswered question at QB.