FS SS WL ML SL CB E T T E CB SE T G C G T TE Q FL F R
At the outside edge of the defensive line are two guys, the defensive ends. Unlike the tackles, who have a job that's very complicated, the defensive ends have a relatively simple job. If it's a running play, their job is to move forward a step or two and make sure the running back cannot get outside of them, where he will have to be chased down by cornerbacks and safeties. They want to make sure the running back is funneled inside to the big crowd of offensive and defensive linemen and linebackers, where he will be slowed down and quickly stopped.
If it's a passing play, the defensive end has the job of getting to the quarterback as quickly as possible and doing anything and everything to disrupt him. Their favorite thing to do is to swat the football out of the quarterback's hands, causing a fumble, then pick up the ball and run for a touchdown. This is very rare, and when it happens it makes the TV highlights for the entire week, and it will also make the team year-end highlight video. Their next favorite thing to do is tackle the quarterback, which is called a sack. Sacks are very good things for the defense. Their next favorite thing to do is to try to jump up at the last second, wave their arms about, and hit the passed football as it flies by, turning a pass into a free-for-all. In short, if it's a passing play the defensive end's job is to create chaos.
Defensive ends must be very fast, so they tend to be somewhat light for a lineman - often 245 to 260 pounds. The most famous defensive end of all time is Reggie White, who weighed about 300 pounds and was incredibly strong and fast. Reggie set the NFL record for most sacks in his career. To this day, many team general managers say if they were to build a defense from scratch, they would want to start with Reggie White, who is regarded by many as the best defensive player ever.
Defensive ends who are good at sacking quarterbacks, getting 10 or more sacks per year, are extremely rare and very valuable. These guys make $5M to $10M per year.
Linebackers are a special breed. They like to torture small animals, drink blood and eat children for breakfast. Linebackers are often quite famous: Ray Nitschke, Dick Butkus, Lawrence Taylor, Mike Singletary, Ray Lewis. These guys are the "enforcers" of the defense. Their job is to make sure that nothing good happens for the offense in the middle of the field, and that the running back has trouble sleeping tonight due to his many bruises and pains.
There are three linebackers, each with a slightly different job. The middle linebacker, ML in the diagram above, is the quarterback of the defense. It's his job to make sure all the other defensive players are lined up correctly and know what scheme they're going to use on the next play to try to stymie the offence. The middle linebacker will also be responsible to see that the running back has no success running between the tackles. In the passing game, if the running back or full back comes into the middle of the field to be an outlet receiver, the middle linebacker's job is to disrupt the pass and make the back regret ever coming into his territory. Middle linebackers rarely have all of their teeth. To a middle linebacker, this is a point of pride. The middle linebacker is often called "Mike," where M is for middle. A middle linebacker will typically weigh 245 to 255 pounds. He has to be a very good runner, as his responsibility on a running play is to be where ever the ball is, either making the tackle or helping.
The strong side linebacker, SL in the diagram above, is to help contain the running back on the strong side of the field. To do this, he must take on the tight end on nearly every play. The strong side linebacker is also responsible to see that the tight end never catches a pass, or if he happens to he winds up regretting it. The strong side linebacker will typically be about as big as the middle linebacker, about 245 to 255 pounds. The strong side linebacker is often called "Sam," where S is for strong side.
The weak side linebacker, WL in the diagram above, is normally a bit lighter and faster than the other two linebackers. He does not wrestle with 265 pound tight ends, or 250 pound straight-ahead running backs like the Sam and Mike linebackers do. His job is to contain cut back running backs who come over to the weak side. He will also help out with coverage in the passing game. Frequently a running back or fullback will come out of the backfield as an outlet receiver. In this case, it will often be the weak side linebacker's responsibility to cover this guy and prevent a pass, or at least tackle the guy immediately. The weak side linebacker is often called "Will," where W is for weak side.