"The Prototypes: Patrick Willis, San Francisco 49ers; Bobby Wagner, Seattle Seahawks
Traditionally, the middle linebacker has been the heart, mind and soul of a defense. Frequently the roughest, toughest player on the field, the middle linebacker was trusted with the most important job: getting to the ball-carrier.
Fending off a fullback or pulling guard and stuffing the running back 10 times a game or more takes a special combination of size, speed, grit, instincts and thirst for violence. Often called the quarterback of the defense, to this day, the middle linebacker usually relays the play calls from the sideline to the huddle.
Now, though, if all a player can do is stop the run between the tackles, he comes off the field in passing situations—and most situations are passing situations.
Today's middle linebacker has to have the size, power and attitude to stop the run when called upon, but it's more important to have the athleticism to cover the middle of the field—whether in man-to-man against running backs or patrolling the middle of the field in zone coverage.
Players that excel at both, like Patrick Willis, are rare and valuable indeed. For most teams, though, inside linebackers who are "good enough" tacklers and very good in coverage are sufficient and plentiful."