The biggest weakness is the inability so far to win road games against good teams, see Washington, NY Jets, and Carolina. Even though Seattle has been plagued by injuries and hasn't really played well on offense or defense all year long, the game @ Seattle on the 16th will tell a lot about this team IMO.
The 12th man will be loud as always, and how the Cardinals perform on a short week and on the road in a very hostile environment will tell us a lot about this team. We saw how the Eagles went in and dominated the Seahawks. If the Redbirds do the same, and in just as convincing a fashion, it will be a "statement game."