in a perfect world you carry extra qb's and rb's in case someone gets hurt, in salary cap and roster cap worlds you have to gamble and NOT expect players to get hurt and get the most benefit out of your 53...you don't rotate in QB's during the games, you do rotate in OL, LB's, WR's etc....plus i honestly feel that Cassel is not built for this offense, it is a mobile offense, not a pocket passing qb and it would take too much to rework the playbook and mentality for a couple weeks.