I know a lot of people roll their eyes when they see a thread like this, but lets play the "what if" card for fun:
What if Cassel plays like he did in the second half of the Jets game the rest of the way? He was making the correct reads, going through his progression and threw the ball extremely well. Aside from the long passes (which I blame on timing more than anything) Cassel was money. He even is mobile enough that teams must not completely ignore him otherwise he can run for good yardage. Seriously, if he plays like that the rest of the way, he is a Pro-Bowler. So why wouldn't a team be interested in him even if we franchise him? So many teams out there need QBs.
It's not an impossible scenario. Well, the trade to Minnesota is impossible, not gonna happen. But I'm talking about it's not impossible for him to play well enough to force the Pats to franchise him and then trade him.