4–3 defense
The Giants employed a 6–1–4 basic formation when they shut out the Browns in 1950, but on many plays this became a 4–1–6 in reality, when the ball was snapped, because the ends dropped off the line to afford extraordinary coverage on passesEarly in the history of the National Football League, teams stacked the defensive line of scrimmage with seven linemen, typically using a 7-diamond or the 7-box.
[2][3] The successes of the T formation and the introduction of free substitution, abolishing the one-platoon system, in the 1940s led to the almost universal adoption by 1950 of the five-man line.
By the late 1940s, Greasy Neale's 5–2 Eagle defense was creating problems for offenses with a five-man line and four-man secondary.
The Cleveland Browns won every championship of the rival All-America Football Conference from its inception in 1946 through its final season in 1949.
Defenses knew they had to find a way to stop the spread-out vertical offense of the Browns.
In the mid-1960s, Hank Stram developed a popular variation, the "Kansas City Stack", which shifted the strong-side defensive end over the tight end, stacked the strong-side linebacker over the tackle, and shifted the weak-side tackle over center.
Landry developed a "flex" variation, in order to take advantage of the quickness of his Hall of Fame tackle, Bob Lilly.
The 'flex' was developed to counter option blocking by the offensive lines which had learned to move their heads up defensive linemen to either side to create holes.
The nose tackle's primary job is to stop the run and take on the double team (which is getting blocked by both the center and the weakside or pulling guard) thus freeing up the linebackers to make a play.
[10] He plays a three technique, meaning he lines up on the outside shoulder of the strong side offensive guard.
The job of a three tech is to prevent the run, keep the guard off linebackers, and rush the quarterback on pass plays.
Teams that want to use a standard 4–3 scheme often face a dilemma: there aren't enough great defensive ends to go around.
Ideal 4–3 defensive ends are athletic and agile and their strength is getting up the field quickly and they usually weigh between 265 and 295 pounds (120 and 134 kg).
In most schemes, they are also responsible for keeping the quarterback from rolling out of the pocket to make big running gains.
But players like Von Miller, an elite and undersized defensive end, play strong side linebacker on first and second downs and use their pass rushing ability on passing downs by lining up at stand up defensive end to bring pressure on the quarterback.
Most notably, Monte Kiffin's "Tampa Cover 2" scheme makes high demands on the MLB, requiring him to have above-average speed, and additional skills to be able to read the play and either maintain his central position to help the outside linebackers cover short passes, drop behind the linebackers in coverage and protect the zone of the field behind the outside linebackers from 11 to 20 yards out, or run up to the line of scrimmage to help assist in stopping the runs.
He also has heavy coverage responsibilities, making a good number of today's Will linebackers former safeties.
He must be a quick and smart player, capable of making tackles efficiently as well as reading the play and alerting his team of game situations.
