He was a very odd QB in some respects. Mediocre to slightly better than average under normal circumstances, very good when he had downfield weapons on offense and a good offensive line to protect him, and downright awful in recent years when the team had a awful line.
But one of the best of all time in a tight spot late in a game when engineering a comeback win, for sure.
He finished his career with a win-loss percentage of exactly .500 ... which probably sums everything up perfectly.