A linebacker (LB) is a position on the defense tasked with stopping the offense. He is lined up behind the defensive linemen. Linebackers are usually the captain of the defense as they must be quick to decipher what play the offense is running and act as a result.
The job of the linebacker varies depending on what play is called. They are the first player who should recognize the offense's play. Linebackers have multiple jobs, the main ones being stopping the running back from getting past the defensive line, attacking the quarterback, and helping defend against passing attempts. Linebackers should be very strong defensive members, but not too large in size where speed is inhibited. Their instincts should be strong because they have to react to their opponent's move in literal seconds!
Like we said before, the main job of a linebacker is to react to many different plays that their opponents throw at them. Sometimes, a player will attempt to sack the quarterback, which is also known as a blitz. If a blitz is called, the linebacker will rush the quarterback to pressure or sack them. If a coverage play is called to defend against the pass, the linebacker will stay back in coverage to help defend the pass. If a coverage play is called, but the offense runs the ball, they must be quick to act to stop the ball carrier from gaining too many yards.