Football Dallas 4-3 Defense
Dallas 4-3 Defense
The 4-3 defensive front is a base defense consisting of four defensive linemen and three linebackers. The man credited with inventing the 4-3 at the professional level is Tom Landry, who coached the Dallas Cowboys from 1960-1988.
Tom Landry Flex Defense
Landry developed an adaptation to the 4-3 known as the “Flex” defense (also known as the “Doomsday” defense). The Flex had a reputation for being one of the most confusing defenses in the history of football, because it changed in real time based on each offensive player’s movement during the play.
The basic concept behind the Flex was to read and react to what the offense was doing as the play happened, rather than attacking certain areas and hoping for the best like regular plays.
Before the snap, the Flex looked like a wacky 4-3 scheme. The strong-side defensive tackle and weak-side defensive end backed off the line of scrimmage a few steps, and the linebackers crept up toward the line of scrimmage.
The Flex was developed to help the middle linebacker stay unblocked so they could make a play on the ball. All the other positions would then stay in a partial-zone run defense, where they were expected to hold down their area and cover blockers while also being ready to react to their opponent. Offsetting the defensive linemen at the line of scrimmage created channels for the middle linebacker to shoot through into the backfield.
Difficulty of the Flex Defense
Despite its on-field success, few coaches ever used the Flex because of its difficulty. The mental strength required by the defense on every play was often much greater than the physical requirements, and coaches found it too confusing and difficult to put into regular use. Though the 4-3 defense remains a constant in contemporary football, the flex adaptation quickly died out.