It really didn't. They faced the 5th most rushing attempts and 16th most passing attempts. You know what that says to me? They faced far too many attempts. On a pure drive-by-drive basis, they were around top 10. And they were 9th in forcing TO's per drive and still faced the 5th most rushing attempts. To me, that screams offensive futility. At the very least, teams rushed on us because we were too hard to pass on. 3rd in passing yards per attempt allowed is REALLY REALLY good when we played Bradyx2, Flacco, Dalton, Brees, Big Ben, Cam Newton, Alex Smith, Tannehill and Matt Ryan. That's a murderer's row of QB's.
The run defense was not good, on the whole, in 2013. But I don't think any coach with a LB group like that and battling their own offense does much, if any, better.
As an aside, our rushing TD's allowed was 8th in the NFL. It's not like teams were blowing through us in the red zone.
People forget how bad the O was that year at scoring. We had 2 games where we scored 30+ points all year. 5 games under 20, and 7 under 21. They were BAD.