Trading for Cassel wasn't that bad. If he turns into a franchise guy you've made a good deal.
The real problem is not even attempting to have a plan B. Our plan B last year was Tyler Palko... to me that's just as bad as having Cassel as a starter. If your QB goes down, which he did... your backup didn't have the arm strength to throw a 20 yard out. Now maybe he fixed that problem this year... we're about to find out with Quinn on Sunday. But he's a huge question mark. He couldn't beat out Tebow... or even Orton.
That's pretty much been Pioli's problem across the board though. As much as people want to rip Belichick, and yeah Brady is the Patriot Way and all that... Belichick was still able to get decent performances out of backup players when starters got hurt. We haven't come close to approaching that level of depth and consistency here.