The Chief is a good guy. Every D-scheme have an Achillies Heel - even Saban's. Once the OC's figure it out they exploit it. Despite some posters' attempt to say otherwise, the Mustang and its variants was his at UT. Most of the 3rd and Chavis first downs came after using that scheme because we never seemed to have two physical CB's with speed on the field at the same time. The OC's would use more protection for the QB, run one side of the secondary down the field, draw the other side to the sideline with a WR or TE, and then send the slot on a deeper crossing or flag pattern over the middle of the field. Sometimes they sent the slot down the field or on a deep out pattern and had the WR do the crossing. Either way it would wind up a first down pass or TD. If the CB's could not mess the timing up or keep up, the safety was out of the picture and it was over.
Ultimately it was Fulmer's fault to even allow that D to be used. Everything else The Chief used or uses is excellent.