First I would like to preface this post with a reminder that I do not consider myself an expert on these concepts and I am attempting to summarize the many articles I have read on the subject. Furthermore, most of these statements are generalizations that do not apply to every NFL snap. The NFL, particularly defense, is all about creating confusion by adding atypical assignments to the typical personnel. Any questions or corrections can be addressed in the comments.
You frequently hear, particularly during the offseason, of team switching from a 3-4 to a 4-3 or vice versa. But ultimately, there are seven players playing near the line of scrimmage, so what is the difference? Why are some players considered 4-3 defensive ends and others are 3-4 defensive ends? What is a "Sam" or "Mike" backer? I would like to answer these questions and more by going over each scheme and each position highlighting their responsibilities on both run downs and passing downs and which player on the Patriots I would consider the starter at that position. I will not go into sub packages such as nickel and dime defenses. Many of the terms in this article are explained in this post, and will be cataloged in the glossary.
Furthermore, if you are confused by my descriptions I highly recommend the following articles for further reading:
Pro Football Focus:
Defensive Line,
Linebackers
Bleacher Report (slightly different terminology)
Wikipedia:
3-4 &
4-3
To start off, I want to get explain some terminology with the help of the figure below. The position where a defensive lineman stands before the snap is called his "technique," the red numbers. Starting from the center and moving outward they range from 0 to 9. Typically, the size (see: weight) of the defensive player decreases as the technique increases, due to the fact the perimeter players need more speed to play in space and the center players are there to clog running lanes and occupy blockers. The offensive line gaps are shown in yellow letters and similarly start at the center and increase outwards. The weak and strong side refer to which side is the "offensive strength," i.e. which side the tight end (TE) is on. This base offense is in a Pro-I-Weak formation; Pro, the quarterback (QB) is under center, I, there are two running backs aligned, Weak, the fullback (FB) is shifted to the offensive weak side.
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| The Red Numbers are the Defensive Lineman Technique. The Yellow Letters are the Offensive Line Gaps. The Circled Letters are the Offensive Positions. |
3-4
A 3-4 stands for 3 down lineman, a nose tackle and two defensive ends, and 4 linebackers, two inside and two outside. In a three man front, particularly under Belichick, the defensive lineman have a two gap responsibility, i.e. the gaps on either side of the offensive lineman they are in front of. The lineman are taught to read and react, by standing up their offensive lineman, reading where the play is going, shed their blocker, and pursue the ball carrier. Furthermore, they frequently require double teams which free up the prowling linebackers to get upfield and make a play. 3-4 defensive lineman do not frequently rack up gaudy stats like sacks, but their presence is shown by making average linebackers good, and good ones great. In general, the 3-4 is built around the massive defensive lineman making the quick, athletic linebackers' lives easier.
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| A prefix of an R or L designates the defensive right or left side, respectively. |
Nose Tackle:
Nose tackles are simply immense. Wilfork, the Patriots' starting nose tackle over the past several years, is listed as ~330 lbs, although most people agree it is probably closer to 350.
Depth Chart: Vince Wilfork (1st round, 2004), Kyle Love (undrafted, 2010), Ron Brace (2nd round, 2009)
Run Defense: In run defense, the nose tackle is the first line of defense. He uses his huge size and elite strength to take complete command of the center and control both A gaps. A team like the Jets who has an equally elite center in Nick Mangold, will often leave this a one-on-one match up, but other teams may need to add a guard to hold him back. This is the best case scenario, as 1) it closes one of the A gaps completely removing it as a running lane, and 2) it removes a potential blocker allowing linebackers to more easily pursue the ball carrier.
Pass Defense: A textbook example of what you want your nose tackle to do against the pass was last years AFC Championship game against the Ravens. That was one of Wilfork's best games of his career. The best way to disrupt a quarterback, particularly a pocket passer like Flacco, is to move him off out of the pocket. Wilfork consistently pushed the Ravens' center back into Flacco's lap which caused him to shift, either to throw on the move, or into the pressure from other defensive players.
Defensive End:
A two-gapping 3-4 defensive end is closer in size to a 4-3 defensive tackle, than a 4-3 defensive end. Like nose tackles, they are a large group of people, typically around 300 lbs, and are trying to occupy space as opposed to penetrate. Richard Seymour was the Patriots' star RDE until he was traded to the Oakland Raiders. Since then, the Patriots had trouble replacing him and I believe it was a significant reason why the Patriots switched to a 4-3 last season.
Depth Chart: Gerrard Warren (12-year veteran FA, signed 2010), Jonathan Fanene (8-year veteran FA, signed 2012), Brandon Deaderick (7th round, 2010), Justin Francis (undrafted, 2012), Myron Pryor (6th round, 2009), Marcus Harrison (5-year veteran FA, signed 2012), Marcus Forston (undrafted 2012)
Run Defense: "Occupy space" is the keyword in run defense. By controlling the tackle (or sometimes guard), the defensive end can read the play, shed the block and make the tackle. If not, he can force the runner to cut back, hopefully, into the linebacker ready to make the tackle.
Pass Defense: The main responsibility of a defensive end in pass defense is containment, especially against a mobile quarterback like Tebow. Typically, on passing snaps one or both of the outside linebackers will be rushing the passer, who will be blocked by an offensive tackle. The offensive guard, therefore, is in charge of blocking the defensive end. If the nose tackle can push the quarterback out of the pocket, he will end up right in the defensive end's lap. Furthermore, by staying disciplined, the defensive end can be ready for a draw play (the quarterback gives a delayed handoff to the running back).
Inside Linebacker:
Inside linebackers in a 3-4 have to be very well-rounded players. They need to do just about everything well: cover, blitz, tackle, read, and most importantly lead. Frequently, one of the inside linebackers will have a headset in his helmet connected to the defensive coordinator calling the defensive plays. For the past 4 years, Jerod Mayo has been played this role as the "quarterback of the defense".
Depth Chart: Jerod Mayo (1st round, 2008), Brandon Spikes (2nd round, 2010), Dont'a Hightower (1st round, 2012), Dane Fletcher (undrafted, 2010), Bobby Carpenter (7-year veteran FA, signed 2012), Niko Koutouvides (9-year veteran FA, signed 2011), Tracy White (10-year veteran, traded 2010), Jeff Tarpinian (undrafted, 2011), Mike Rivera (2-year veteran, signed 2011)
Run Defense: Even though inside linebackers have to do a lot, their bread and butter is run defense. They read the running back and then hit the gap hard meeting any blocker or running back hard. Vicious hitters like Ray Lewis of the Ravens and Patrick Willis of the 49ers have become NFL stars due their ability to find the hole in the offensive line and make explosive plays in the run game.
Pass Defense: While inside backers can be sent on a blitz, they typically drop into coverage. Over the past several years, Belichick has sent inside linebackers on a blitz only 10% of the time. Instead, in man coverage, they match up against running backs. Without a linebacker with good "sideline-to-sideline" speed, defenses can easily get gashed for a huge yardage on a simple dump off play to a running back running towards the sideline. In zone coverage, they are responsible for intermediate throws over the middle. Because these linebackers are so ready to attack the line of scrimmage to tackle a running back, they are frequently the most affected by play action plays, leaving the zone they are responsible for wide open.
Outside Linebacker:
Outside linebackers in a 3-4, particularly the right outside linebacker, are the teams top pass rushers. James Harrison of the Steelers, Tamba Hali of the Chiefs, and Clay Matthews of the Packers are all NFL elite pass rushers at the outside linebacker position. They are typically the tallest players on defense (6'3"-6'5") with long arms to combat offensive tackles equally long arms. They need a combination of speed to rush the passer, strength to shed blocks in the run game, and quickness to drop into coverage.
Depth Chart: Chandler Jones (1st round, 2012), Rob Ninkovich (7-year veteran FA, signed 2009), Trevor Scott (5-year veteran FA, signed 2012), Jake Bequette (3rd round, 2012), Jermaine Cunningham (2nd round, 2010)
Run Defense: In run support, outside linebackers will usually be blocked by a tight end whom they must jack up and shed if the run heads in their direction. If the run is to the opposite side and there is no tight end to block them (weak side outside linebacker), they use their quickness to pursue from the back side to tackle from behind, but must be careful not to be too aggressive and over pursue allowing a cut back.
Pass Defense: Pass rush. The defensive ends provide containment, the nose tackle pushs the quarterback out, and the outside linebackers get after the quarterback. Although they will frequently drop into coverage too, in 2010, when they ran a 3-4 as their base defense, Belichick sent at least one outside linebacker over 80% of the time. Now that may have been a product of their awful defense and inability to get pressure with just three lineman, but that is not against the norm, particularly in today's pass happy NFL. In zone coverage, outside linebackers are responsible for either the flat (outside short area 0-4 yards off the line of scrimmage) or the outside intermediate area (5-12 yards off the line of scrimmage). Whereas, they typically are asked to cover tight ends in man coverage.
4-3
A 4-3 stands for 4 down lineman, two defensive tackles and two defensive ends, and 3 linebackers, the Mike, Sam, and Will linebackers. In a four man front, the defensive lineman have a one gap responsibility. This is a slightly more aggressive approach as it typically sends all four lineman through a specified gap attempting to penetrate to disrupt running plays or get pressure on the quarterback, imposing the defenses will on the offense, as opposed to reacting to it. Also, the line is less symmetric with respect to the offensive formation compared to the 3-4.
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| Again, a prefix of an R or L designates the defensive right or left side, respectively. |
Defensive Tackle:
Like the interior lineman in a 3-4, 4-3 defensive tackles are typically around 300 lbs. But instead of standing up their offensive lineman and shedding their blocks after reading the play, they instead rely on their quick first step to create a sudden burst past their lineman. The defensive tackles play as a 1- and a 3- technique, responsible for an A and a B gap, respectively. The best lineman have a wide variety of tactics to win their one-on-one battles, including the swim, just as it sounds swinging the arms like the forward stroke to get behind the offensive lineman, the bull rush, getting under the opponents pads and rocking him back onto his heels then pushing him backwards, or the spin move, catching the lineman leaning and then spinning past him into the backfield.
Depth Chart: Vince Wilfork (1st round, 2004), Kyle Love (undrafted, 2010), Jonathan Fanene (8-year veteran FA, signed 2012), Brandon Deaderick (7th round, 2010), Ron Brace (2nd round, 2009), Myron Pryor (6th round, 2009), Gerrard Warren (12-year veteran FA, signed 2010), Marcus Forston (undrafted 2012), Marcus Harrison (5-year veteran FA, signed 2012)
Run/Pass Defense: For defensive tackles, the goal is usually the same regardless of a run or a pass play: get into the backfield and disrupt the play. In general, these defensive lineman have fewer reads of the offense and instead try impose their strengths to make the offense react. There are wrinkles, such as stunts where two lineman switch gaps after the snap trying to confuse the offensive lineman or a tackle dropping into a shallow zone coverage, but ultimately tackles try to get in the backfield and cause problems.
Defensive End:
4-3 defensive ends are slightly leaner than their 3-4 counterparts, between 260 and 280 lbs. They too focus mostly on getting behind their respective lineman utilizing many of the same moves. The spin move was practically patented by pass rushing extraordinaire Dwight Freeney of the Indianapolis Colts. The defensive ends play as a 7- and a 9- technique, responsible for either both C gaps, or a C and a D gap, respectively.
Depth Chart: Chandler Jones (1st round, 2012), Rob Ninkovich (7-year veteran FA, signed 2009), Jake Bequette (3rd round, 2012), Trevor Scott (5-year veteran FA, signed 2012), Jermaine Cunningham (2nd round, 2010), Justin Francis (undrafted, 2012)
Run/Pass Defense: Similarly to defensive tackles, defensive ends' mantra is get into the backfield to apply pressure. In the run game, they are responsible for containment to prevent outside runs. In the passing game, these are the teams top pass rushers, similar to the OLB in a 3-4. Some defenses, such as the Philadelphia Eagles have both of their defensive ends as 9-techniques, which makes them incredibly difficult to block on passing downs, but creates larger gaps in the run game which puts stress on the outside linebackers. Not surprisingly, the Eagles were tied for the league lead in sacks.
Weakside (WILL) Linebacker:
The Will backer is the coverage coverage backer. The smallest of the three linebackers, he is the most likely to drop into man or zone and use his speed to track down running backs in the open space or step in front of shifty slot receivers.
Depth Chart: Jerod Mayo (1st round, 2008), Tracy White (10-year veteran, traded 2010), Mike Rivera (2-year veteran, signed 2011)
Run Defense: In gap assignment, the Will will be in charge of the weak-side B gap, but can also go over the top of the defense if the run is to the opposite side. As always, over pursuit over the top can be dangerous as a cut back to the now undefended gap can lead to big plays.
Pass Defense: The Will backer is the most free range in coverage. His speed is his greatest asset. Due to the tight end being on the opposite side of the formation, the Will usually is in charge of the running back or full back in man coverage, while protecting the middle of the field in zone. The Will may also have the freedom to rush the passer from a variety of places, although Belichick prefers him to stay in coverage. He sent Jerod Mayo, the start Will backer in 2011, on pass rushing snaps only 11% of the time despite having significant success when he was sent.
Middle (MIKE) Linebacker:
The Mike backer is a "thumper." The run stopper. The guy that loves to hit hard.
Depth Chart: Brandon Spikes (2nd round, 2010), Dane Fletcher (undrafted, 2010), Jeff Tarpinian (undrafted, 2011)
Run Defense: In gap assignment, the Mike backer gets the strong-side A gap. He is ready to get "downhill" and shoot into the backfield, knock off a blocker, and make a tackle on inside runs.
Pass Defense: In standard zone defense, like a Cover 2, the Mike backer covers the intermediate routes over the middle of the field. However, in the Tampa-2, there is significant more strain on the Mike to drop quickly into a much deeper zone to prevent the seam route (a route Gronkowski lives off of) that is able to defeat the Cover 2 if run properly. In man coverage, it is more common for the Mike to cover either the running back or full back. The Mike blitz was also rarely used last year, ~15% of the time.
Strongside (SAM) Linebacker:
The Sam is the pass rusher of the three. The largest and best equipped to take on offensive tackles or pass blocking tight ends, the Sam backer will use a combination of power and speed to get after the quarterback. He will also typically be the closest to the line of scrimmage.
Depth Chart: Dont'a Hightower (1st round, 2012), Bobby Carpenter (7-year veteran FA, signed 2012), Niko Koutouvides (9-year veteran FA, signed 2011)
Run Defense: In gap assignment, the Sam will get the strong side C or D gap depending on whichever one the defensive end doesn't hit.
Pass Defense: In man coverage, the Sam backer will often cover the tight end; whereas in zone he will cover outside short-intermediate routes. But most frequently, particularly under Belichick, the Sam will go after the quarterback. Rob Ninkovich, the starting Sam backer in 2011, rushed the passer 64% of passing plays.
