I hammered Cassel before the trade and his first season, and for good reason. But last year he dusted himself off and had a pro bowl season.
The fact that you mentioned in your post that you are down on Cassel shows that you havent been paying attention.
This makes your opinion on Stanzi more than suspect IMO. Let the kid play as a backup before you start screaming about the sky falling. It cant be any worse than what we have had in any recent season.