As usual, one of the main goals that the Pittsburgh Steelers defense had going into the Sunday game against the Minnesota Vikings was to stop the run and to do so they were forced to use safety Troy Polamalu either inside the box or within 5-7 yards from the line of scrimmage on 48 of the 52 defensive snaps. That run stop commitment did not work that well, however, as Vikings running back Adrian Peterson still managed to run for 140 yards in the game on 23 carries.
In addition to not being able to stop the run with eight men in the box, having Polamalu that close to the line of scrimmage most of the time meant the defense was forced to play the cornerbacks off the line of scrimmage in either a cover-1 or cover-3 look not only on first and second downs, but a lot of third downs as well. This in turn gave Vikings quarterback Matt Cassel the opportunity to complete a lot of short passes and generally kept him away from facing a lot of third and long situations.
When the Vikings offense was faced with third down and five yards or more to go in the game, the Steelers defense got off the field five out six times. It would have been all six times had they recovered the fumble that linebacker LaMarr Woodley caused on his sack of Cassel.
On the flip-side, however, when the Vikings offense faced third downs with less than five yards to go, they converted four times out of five opportunities with one of those being the 70 yard touchdown by wide receiver Greg Jennings.
The Vikings ran 24 total first down plays in the game and averaged 7.5 yards on them. If you discard the 60 yard touchdown run by Peterson and the late kneel down by Cassel, they still allowed and average of 5.55 yards on the 22 other first down plays and that is what kept the defense behind the chains all game and Polamalu near the line of scrimmage.
To better illustrate this, the Steelers were only able to use their sub package defense in the game 19% of the time. That resulted in rookie linebacker Vince Williams having to play 43 out of 52 plays.
Until the Steelers defense can get back to stopping the run successfully on first down without having to commit Polamalu so many times to the box, they will more than likely continue to have the problems that they had Sunday. These problems become even bigger when they fail to tackle well like they did in London.
Polamalu can't make plays in the secondary when he's boxed up and that's exactly what he was Sunday against the Vikings.