Don’t let the defensive yardage totals fool you: the Cowboys defense is bad. In looking at DVOA, a more accurate way of measuring defensive success, the Cowboys rank 20th in defensive DVOA, 16th in run defense DVOA, and 24th in pass defense DVOA. They also have the fifth-weakest schedule according to Football Outsiders’ DVOA-based rankings.
While some of that is simply due to poor performances from players - Leighton Vander Esch led all linebackers in missed tackles before his injury, and Chidobe Awuzie has been easy to pick on in coverage - a lot of it stems from coaching and, more importantly, the scheme.