We tend to focus on the players when the team is losing but I am starting to think Brian Baldinger hit the nail on the head with his recent comments about the Cowboys attention to details. It's the little things. Not running crisp route (Aikman), not running crisp stunts (Baldy), maintaining gap integrity, staying on blocks or just getting to the assigned guy to block, etc. All these things wind up costing the team. I watch other teams run screen plays and they manage to get a blocker on every defender to free the ball carrier for good yardage. Dallas runs a screen and it's a negative play.
Its been this way for a while. I read once that Vince Lombardi had his team run that famous power sweep play over and over in practice till they got it perfect. Not just good, it had to be perfect in every aspect. The Packers could run that play when every opponent knew it was coming and yet they could not stop it consistently. The Packers execution was always near perfect. I have no idea how the Cowboys practice but I get the impression they run a play a couple of times and move on to something else. They just look like they are a sloppy team. Missing blocks on offense, missing tackles on defense. Offensive linemen not picking up the stunt or twist and defensive linemen and LBs not maintaining their gap control. It's just poor execution, but when coupled with players who are not that good to begin with the result is 47-9.