Washington was mentally expended with their "franchise" QB permanently benched. The Colts was a complete fiasco that started wrong and went downhill fast. Neither team had defenses capable of limiting the Cowboys offense.
The playoffs changed all that.
Think of the finish in Green Bay when they allowed 26 points and 416 yards of offense to a gimpy Rodgers despite DeMarco Murray rushing for 123 yards and the offense gaining 21 first downs. In that game they were dealing with issues at every level of the defense (no Melton, no Terrell McClain, Rolando McClain ankle hurt+concussion, Hitchens' ankle hurt, Mincey with a concussion, and of course no Durant, Lee or Claiborne). We're talking an utterly jacked up facsimile of what the front office intended when the offseason started.
And the 20 given to Detroit doesn't account for the 397 yards of offense allowed.
In each playoff game Dallas had just 315 and 318 yards of offense. Clearly the offense was limited in each by the defense allowing long drives.
Basically they were a worn out unit by seasons' end.
That has to change, hopefully the additions and return of Lee will change it.