Couple of points however

1. The spread tends to balance off the defenders versus offensive players from 11 defenders vs 10 + the QB. Most defenses use 1 or 2 safeties to support cornerbacks and avoid 1 on 1 coverage or go to a zone scheme. It's the classic choose what you want to try and stop, and I'll exploit it.

2. The defense often chooses to use lighter and faster players to cover the wide-open field, and unless you're stocked with JOKs, you become vulnerable to being pushed around.

3. Alabama has had a succession of big and somewhat fast backs that take advantage of defenses against the spread. Saban can kill other teams by having superior passing games (mainly the WRs) and running games. I think it's more than what keeps the defenses honest, but what the defense allows him.

4. As you pointed out in your original post, a good offense requires players and schemes to stretch the defense and to gain chuncks on the ground.

4.