Their defense is still going to be great which is why most think they'll still be very tough.
Their offense I believe is going to struggle early because Nicks won't be able to replace Plax, production wise, right away and the rest of the receivers won't scare anyone. Jacobs will find a lot more company around the line, at least early on, so they're going to have to really lean on their defense to win games for them for at least the first couple of months of the season.