The strong side linebacker, or Sam Linebacker, is a versatile run and pass coverage backer in a 4-3 defense. He needs to provide strong run support and fill his gap on the run, but he also is required to drop in short zones in both cover 2 and cover 3. At times, he will also play man-to-man coverage on either the tight end or the number two or three receiver. Depending on the tendencies of the teams you play, your Sam linebacker might be more of a pass coverage guy, or more of a traditional "linebacker" type. Either way, versatility and speed are critical traits for a good Sam Linebacker.
Here's your alignment, assignment and key for Sam Linebacker.
The Sam linebacker will line up on the strong side of the formation, about seven to eight yards back from the tight end, if the offensive formation has one. If there is no tight end, the Sam linebacker will essentially split the space between the end man on the line of scrimmage and the inside slot receiver. This allows him to be in close proximity to stop the run, and in good position to drop in pass coverage if necessary.
The Sam's responsibilities are to fill his assigned gap (which will be different if the play flows towards him or away from him) on the run. He can't waste any steps in his pursuit of the football. He also has pass coverage responsibilities which vary from covering the tight end, or the back out of the backfield, to dropping to the deep hook/curl zone.
The Sam will get his initial key from the tight end. If the tight end blocks hard, it's an initial run read. If he releases, or looks like he's trying to separate from the defensive end, it's likely a pass read. The Sam also needs to have his eyes to the backfield to see whether it's flow to, or flow away. This will help him determine his assignment as well.
If the Sam has a run read, he will play good gap defense, and fill his assigned gap, without wasting steps, moving downhill as quickly as possible. If it's flow away, the Sam usually is assigned the cutback "A" gap, flowing inside out and watching for the back to cut back.
If it's a pass read, the Sam will cover his assigned man, or drop into zone coverage. If it's zone coverage, he will keep his head and eyes on the quarterback as he drops to break on the ball if it's thrown his direction.
Sam linebackers make a huge impact on the game. Like strong safeties, they wear different hats depending on down and distance, and the scheme of the opponent.