I don't think he actually is physically fragile. He plays kamikaze style. He tore up his knee on a play where he stupidly ran upright into the endzone between two defenders, who unsurprisingly managed to disable him. The situation didn't require that and a normal QB would have slid, dived in the direction of the pylon or gone out of bounds or not attempted that play at all. It was a stupid injury, but I think most guys hit like he was hit would have been injured. He then continued to play after the injury, undoubtedly aggravating it. His refusal to throw the ball away, get rid of it downfield in reasonable time, or run out of bounds added numerous, what I'll call 'voluntary' hits. His problems were mental, not the result of a fragile body. He never really learned that NFL defenders are better than the guys he faced in a minor college league and that he couldn't get away with what he got away with in college. He was stubborn, seemingly stupid, and in his last season had poor receivers and a poor OL. He lost his mobility through that goal-line hit. Then, what seemed to be a very severe concussion, because he refused to slide. Dirty hit, despite no call, but his style of running enabled it.
I guess I should say foolish and stubborn rather than stupid, he seems reasonably intelligent, he just never played that way.
