Well you have to know your assignment, but you should also know when you can cheat your assignment to make a play. Great players do this all the time. Stille was probably responsible for the running back on the play, but it's also immediately obvious he wasn't going to be able to do a damn thing about the running back on the play and him following the running back down the line accomplished nothing even if the qb had handed the ball off. Even if Stille just sits where he is, that could have slowed the qb down enough to prevent a big play. Stille should have known he wasn't going to be able to do anything about the running back, but he could have done something about the qb, even if it wasn't his assignment. The same thing for Young. Instead of just standing there in no man's land not really covering the receivers, he could have made a play on the qb.
He wasn't responsible for the running back. We had the playside accounted for with other defenders. The things the backside DE on this play has responsibility for us closing/narrowing the cutback lane, prepare for a wham block (didn't happen here), and prepare to play the QB pull.
This is general run game technique for a DE on plays away from you:
1) on snap, when you don't get touched,
STOP. There is a reason you aren't getting pressure on your shoulder from an OL. You're either the player being read or the player targeted for a kick-out block.
2)
stay shallow, don't get depth - this means you pop your feet and keep them ON the line of scrimmage. Depth in the backfield kills you, aka puts you in no man's land - you are easily kicked out by a pull or wham block, you open the gate on the cutback lane, the QB doesn't have to work as hard to get around you.
3)
keep hips and shoulder upfield while shuffling along the LOS, trying to get your left hip as close as possible to the left hip of the nearest OL. If you have a wham block or pulling OL coming your direction, staying shallow to the OL allows you to wrong shoulder the block and bounce the cutback to your pursuit. If you stay shallow and the RB cuts back, you're ready to make the tackle or chase him to your pursuit. If the QB pulls the ball on the read, you are prepared to change direction and run directly down the LOS to stretch the play as far as you can.
I can't speak for what happened with the safeties behind the DL and LBs, but Stille didn't execute his technique. Had he done it, the QB probably gives the ball, and we have it bottled up.