Yeah, they probably do. When was the last time a starting quarterback who played well was replaced when he wasn't injured? Doesn't happen very often. Coaches might say th ejob is open, but it usually isn't. Lots of reasons why. among them, it is good to have predictability, it is good to have a guy with game experience which you can't simulate no matter how you try, especially if he plays well. And it is hugely risky to replace an established starter. And most coaches are decidedly risk averse. Heck, they even have to have a card that tells them when to go for 2 points. Replacing the established starter risks messing with team chemistry, dividing the team into the Hernadezes and the Boneses. And if it doesn't work out, a coach can lose more than face.