The play that really did the Pittsburgh Steelers in on Sunday in their loss to the Miami Dolphins was the 55 yard run by running back Daniel Thomas on 2nd and 1 with 3:59 remaining in regulation. The blame for the big run goes squarely on the shoulders of linebacker LaMarr Woodley and safety Troy Polamalu, who you can pretty much call an inside linebacker these days.
As the animated gifs show you, this is the old power ride stretch play. At the snap, Woodley allows himself to get hooked by Dolphins tight end/h-back/fullback/pilot/MC Charles Clay. Even though safety Will Allen gets buried by the pulling left guard in a mismatch, at least he takes on the block and keeps Thomas inside of him. It doesn't look pretty, but you have to commend him for taking the punishment.
As far as Polamalu goes, he too is mismatched against pulling center Mike Pouncey, but he has to get over the top of him and across his face in order to force Thomas inside to down-the-line pursuit. The inability of Woodley and Polamalu to do their jobs results in both interfering with defensive end Cameron Heyward being able to make a play.
While we are at it, cornerback Ike Taylor is also slow to get off of the stalk block of wide receiver Brian Hartline and all he can do is stick out one arm on Thomas as blows right up the open lane.
This is what happens when you have players playing outside of their normal position. Woodley over the years has been pretty solid at setting the edge at his usual left outside linebacker spot, but he failed miserably on this play when lined up on the opposite side. As for Polamalu, he's a safety, not a linebacker.
I'm willing to bet you see other teams try this play, or some variation of it, over the course of the remaining thrree games. The Dolphins ran it out of a hurry-up offense and against a defense that was spread out and not loaded up in the box. It was a great play call and it essentially won the game.