Gotta show it in practice before you deserve a shot on the field. I'm not a believer in someone all of a sudden just 'turning on the switch' in a live game scenario. There may be some players like that out there, but, they're a minority and often times not worth the risk unless you're put in a situation where you have to use them. I mean, if you're not reading defenses well in practice, or not managing the huddle well, or you're throwing picks, or any other negative thing, you're probably going to keep doing it in a game.