We go over this again and again, but the fact of the matter is that as a starter he ranged from okay to laughably bad (Denver). His QBR for his four starts was 66.5, 55.6, 29.1, and 66.8. And it's not like he was some green rookie that got thrown to the wolves; he was a 3rd year player who had studied behind one of the greatest QBs of the generation.
He just hasn't shown anything to suggest that he is a great NFL QB.