Linebacker A linebacker ( LB ) is a position in American football that was invented by football coach Fielding H . Yost of the University of Michigan . Linebackers are members of the defensive team , and line up approximately three to five yards ( 4 m ) behind the line of scrimmage , behind the defensive linemen . Linebackers generally align themselves before the ball is snapped by standing upright in a " two point stance " ( as opposed to the defensive linemen , who put one or two hands on the ground for a " three point stance " or " four point stance " before the ball is snapped ) . The goal of the linebacker is to provide either extra run protection or extra pass protection based on the particular defensive play being run . Types . Middle linebacker . The middle or inside linebacker ( MLB ) , sometimes called " Mike , " is often referred to as the " quarterback of the defense . " Often it is the middle linebacker who receives the defensive play calls from the sideline and relays that play to the rest of the team – and in the NFL he is usually the defensive player with the electronic sideline communicator . A , the middle linebacker can be asked to blitz ( though they often blitz less than the outside linebacker ) , cover , spy the quarterback , or even have a deep middle - of - the - field responsibility in the Tampa 2 defense . In standard defenses , middle linebackers commonly lead the team in tackles . The terms " middle " and " inside " linebacker are often used interchangeably ; they are also used to distinguish between a single middle linebacker playing in a 4 – 3 defense , and two inside linebackers playing in a 3 - 4 defense . Outside linebacker . The outside linebacker ( OLB ) is usually responsible for outside containment . This includes the strongside and weakside designations below . They are also responsible for blitzing the quarterback . The " OLB " is often found responsible for benefiting the team on defensive points allowed . Strongside linebacker . The strongside linebacker ( SLB ) is often nicknamed " Sam " for purposes of calling a blitz . Since the strong side of the offensive team is the side on which the tight end lines up , or whichever side contains the most personnel , the strongside linebacker usually lines up across from the tight end . Often the strongside linebacker will be called upon to tackle the running back on a play , because the back will be following the tight end ' s block . He is most often the strongest linebacker ; at the least he possesses the ability to withstand , shed , and fight off blocks from a tight end or fullback blocking the backside of a pass play . The linebacker should also have strong safety abilities in pass situation to cover the tight end in man on man situations . He should also have considerable quickness to read and get into coverage in zone situations . The strongside linebacker is also commonly known as the left outside linebacker ( LOLB ) . Weakside linebacker . The weakside linebacker ( WLB ) , or the " Will " , must be the fastest of the three , because he is often the one called into pass coverage . He is also usually chasing the play from the backside , so the ability to maneuver through traffic is a necessity for the Will . The Will usually aligns off the line of scrimmage at the same depth as Mike . Because of his position on the weakside , the Will does not often have to face large interior linemen one on one unless one is pulling . In coverage , the Will often covers the back that attacks his side of the field first in man coverage , while covering the weak flat in Texas Loop or hook / curl areas in zone coverage . . Formations . The number of linebackers is dependent upon the formation called for in the play ; formations can call for as few as none , or as many as seven . Most defensive schemes call for three or four , and they are generally named for the number of linemen , followed by the number of linebackers ( with the 46 defense being an exception ) . For example , the 4 - 3 defense has four defensive linemen and three linebackers ; conversely , the 3 - 4 defense has three linemen and four linebackers . 4 - 3 defense . In the 4 - 3 defense there are four down linemen and three linebackers . The middle linebacker is designated " Mike " and two outside linebackers are designated " Sam " and " Will " according to how they line up against the offensive formation . If there is a strong call , the linebacker on the strongside is called " Sam " , while the linebacker on the weakside is called " Will " . The outside linebacker ' s job is to cover the end to make sure a run doesn ' t escape , and to watch the pass and protect from it . The middle linebacker ' s job is to stop runs between the tackles and watch the entire field to see the play develop . On pass plays , the linebackers ' responsibilities vary based upon whether a man or zone coverage is called . In a zone coverage , the linebackers will generally drop into hook zones across the middle of the field . However , some zones will send the outside linebackers into the flats ( area directly to the left and right of the hash marks , extending 4 - 5 yards downfield ) . In a man - to - man call , the " Sam " will often cover the tight end with help from a safety over the top , while at other times , the " Sam " and " Will " will be responsible for the first man out of the backfield on their side of the center , with the " Mike " covering if a second man exits on that side of the field . In the " Tampa 2 " zone defense the middle linebacker is required to drop quickly into a deep middle zone pass coverage thus requiring a quick player at this position . 3 - 4 defense . In the 3 - 4 Defense there are three lineman playing the line of scrimmage with four linebackers backing them up , typically two outside linebackers and two inside linebackers . The weak side inside linebacker is typically called the " Will , " while the strong side or middle inside linebacker is called the " Mike " . " Sam " is a common designation for strong outside linebacker , while the other position is usually called " Jack " and is often a hybrid DE / LB . Usually , teams that run a 3 - 4 defense look for college defensive ends that are too small to play the position in the pros and not quite fluid enough to play outside linebacker in a 4 - 3 defense as their " Jack " linebacker . The idea behind the 3 - 4 defense is to disguise where the fourth rusher will come from . Instead of the standard four down - linemen in the 4 - 3 , only 3 players are clearly attacking on nearly every play . A key for running this defense successfully is having a defensive front of three large defensive linemen who command constant double teams . In particular , the nose tackle , who plays over the offensive center , must be able to hold ground and to occupy several offensive blockers in order to allow the linebackers to make plays . The focus of the 3 - 4 defensive line is to occupy offensive linemen thus freeing the linebackers to tackle the running back or to rush the passer or otherwise drop into pass coverage . Generally , the primary responsibilities for both outside linebackers are to stop the run and rush the quarterback in passing situations , in which they line in front of the tackles like true defensive ends . The outside linebackers in a 3 - 4 defense are players who are very skilled are rushing the quarterback and they would be playing defensive end in a 4 - 3 defense . When it comes to the inside linebackers , one is generally a run stuffing player who is better able to handle offensive linemen and stop running backs when the offense features a running play , while the other is often a smaller , faster player who excels in pass coverage . However , the smaller or cover LB should also be able to scrape and plug running lanes decently . The design concept of the 3 - 4 defense is to confuse the offensive line in their blocking assignments , particularly in pass blocking , and to create a more complex read for the quarterback . Many 3 - 4 defenses have the ability to quickly hybrid into a 4 - 3 on the field . 46 defense . In the 46 defense there are four linemen , three linebackers and a safety who is moved up behind the line of scrimmage . Thus it appears as if there are 4 linebackers , but it is really 3 linebackers with one safety playing up with the other linebackers . Three of the defensive linemen are over both of the offensive guards and the center , thereby making it difficult to double team any one of the three interior defensive linemen . This can also take away the ability of the offense to pull the guards on a running play , because this would leave one of the defenders unblocked , or , at best , give another lineman a very difficult block to make on one of the defenders . The safety , like the linebacker , can blitz , play man - on - man , play zone , or drop back into deep coverage like a normal safety would do . The 46 is used in heavy run situations to stop the run , when a team wants to bring lots of pressure , or merely to confuse the quarterback and offensive line . In the 46 both outside linebackers play on the strong side ( the side with the tight end ) . One of the linebackers plays in front of the tight end , while the other linebacker plays on the outside of him . The middle linebacker plays as a traditional linebacker approximately 5 yards off the line of scrimmage , with the strong safety next to him . Buddy Ryan is generally regarded as the originator of this defense , developing it and using it with great success with the 1985 Chicago Bears . It was named in honor of Chicago Bears safety , Doug Plank who wore the number 46 . Today this defense is rarely used as a base defense due to the increased use of spread offenses and multiple receiver sets , but it may be used occasionally to confuse the offense . 4 - 4 defense . This defense is effective at run - stopping but is weaker than a 4 - 3 defense at pass coverage because it uses only three defensive backs . One of the outside linebackers is usually called into either blitz or pass coverage in order to make up for the missing DB . In the NFL and college , this alignment is used mainly in short yardage situations or near the goal line . It is commonly used in high school football .