A few weeks ago, Jeff Cavanaugh of 105.3 The Fan floated the idea of drafting a special player like CJ Mosely (LB, Alabama) to play the Middle, or Mike Linebacker position, allowing the incumbent Mike and unquestioned leader of the Cowboys defense, Sean Lee to move to the Weakside, or Will Linebacker position with hopes of changing the ever concerning trend of Lee's struggles to stay healthy and on the field. But what exactly is the benefit of having Lee outside as opposed to the Mike?
Let's take a look at the Cowboys base front to get an idea.
As you can see, here the LBs in the front fill the "bubbles" in the DL between the NT (or one-technique) and the closed DE on the one side, and the and the Nose and the Under Tackle (three-technique) on the other. If we generalize that most runs will be called to the strong side, we can see how the alignment of the MIKE would open him up to blocks from the play side guard on a zone run, the FB on an ISO or Lead and the pulling guard on a Power Run.
As we continue, in general the offense has a numbers disadvantage in the running game, because the QB is not a blocker or a threat to run in most cases, therefore many times offenses have to be selective and are not able to account for every defender. Most times they will leave the player farthest from the call unblocked, which will be the WILL or the Open End.
This is why I talk a lot about this scheme needing a "run & hit" LB at the Will position, having a guy with the instincts, speed, and tackling ability to become a factor on the play side in the run game is major asset for an Under front defense. And playing Sean Lee at the WILL instead of the MIKE would take him out of traffic, thereby reducing the injury risk inherent in constantly being targeted by blockers focused on taking the MIKE out of the play.