I don't think it's just one thing, but multiple things. To start, I again point to the play of the DL... it has been sub par relative to the talent. And while the play of the DL is important, regardless of scheme, inconsistent and poor play lends to bad things happening in this system. I think on the back end, the problem is twofold, and the first isn't really a problem, so much as a necessary reality of the situation... you've got some young players, green behind the ears that are getting put into some tough situations. There's going to be some cuts received there, simply because of that. Over time, that will, or certainly should, improve. On the other hand, and more concerning to me, the play of Moore and Saab has been a bit more inconsistent overall than I was expecting. Perhaps my expectations were too high though, and it is fair to point out, that it's a new system for both. However they should be playing pretty fast in it at this point, IMO.
Lastly, for the last 6 quarters, Wommack has looked reactionary, at best. He's got to find some ways to get stops when it matters. As bad as the DL has been at times. As bad as the backend has been at times. Hell, as bad as the luck in some cases has been at times... Wommack appears to have a pretty weak grip on things right now. Whether he realizes it or not, and I'm sure he does, there is a substantial amount of pressure on him at this point to get this defense molded into a solid unit. They don't have to be top 10 with the caliber of the Bama offense, but what they can't be is weak to the point that they put them team in hole after hole, week after week.