My honest answer is that I have no freaking idea. I haven't seen enough of Cassel to know if he has potential to improve, and I feel he will need to improve significantly if they are going to win at least 10 or 11 games.
I am also not really sure where our defense is right now. They looked pretty good the first two weeks and absolutely terrible last week. Will the real Pats D please stand up?
As BB says, every year is different. Last year the D was always getting plenty of rest while the offense set their records, and they were usually playing with the lead. Both of those things tend to distort their performance toward the positive. Of course there have been a couple of personnel changes as well (O'Neil for Samuel and Mayo for Seau amongst the starting lineup). So honestly, I do not feel that I know the answer to this question, one way or the other.