Another critical thing to know when it comes to pass protection and the run game is how to identify the middle linebacker (mike). When the defense is in base personnel (4 DL, 3 LB’s, 4 DB’s- could also be 3-4-4), it is easy as the mike is the middle of the three linebackers. The strong side of the formation is the side with the tight end. Thus, the two other linebackers are the sam and will.
In a nickel defense (4 DL, 2LB’s, 5 DB’s- could also be 3-3-5) it is a bit harder as a defensive back has come into the game, replacing a linebacker. So, he is usually detached from the box, and thus away from the two linebackers. The box is from one side of the line to the other, so if there is no tight end attached, it’s everything inside each of the tackles. In the image above all three LB’s are within the box.
In the example below the Sam LB is the strong safety as the Cardinals are in nickel personnel.
Quite a lot of the time the offense, either the quarterback or center, identifies one of the outside linebackers (Sam or Will), instead of the mike. However, if you can identify the mike, you can identify the Sam or Will.
So, in summary, the Mike LB is the middle of the three linebackers. If it’s a nickel defense, it’s the middle of the three defenders closest to the box.