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Defensive Line Technique and the 4-3 Over Front

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Kim Klement-USA TODAY Sports

The offseason is dark and full of terrors. If you're like me, then Clemson football takes precedence over every other sport. Basketball season? You mean bowl and recruiting season. Baseball season? No, that's spring practice. STS prides itself as the best source for Clemson football analysis, and a major part of it is due to our focus on the details and nuances of football to educate our readers. For those of you desperate for your football fix, I decided to go back to the basics and attempt to explain Clemson's base defensive strategies from the ground up.

The defensive reviews written during the season merely narrated the formation (based on personnel, like 4-3 or nickel) and play call, but did not detail the defensive alignments  -- like I said, football is incredibly nuanced and STS differentiates itself with the details. So why not go all in on them when there is time during the offseason?

I will divide this into a series of articles throughout spring practice separated by position group, and here we obviously begin with the defensive line. In this entry I will outline relevant terminology and techniques before I explain Clemson's base defense: the 4-3 Over.

Gap and Alignment Terminology

Below is your basic chart which outlines the specific alphabetized gaps and the numerical defensive line techniques where the defensive linemen align at the snap. Use it as a reference for the remainder of the article.


To reiterate: the A gaps are on either side of the center, B gaps between each guard and tackle, and so forth. The alignment techniques are similarly simple: even numbers refer to an alignment directly across from an offensive lineman; odd numbers refer to an alignment across from the shoulder of an offensive lineman. When you see the "War Daddy" label it means a massive 0 or 1 tech DT who can blow up the interior OL.

For example, a 1 tech will align himself across from the inside shoulder of a guard and a 3 tech on the outside shoulder of a guard, whereas a 2 tech aligns "heads up" or directly across the face of a guard. This is from where the terms odd tech (aligned in gaps) and even tech (aligned heads up) derive.

Gap Technique

The first step in the implementation of a defensive philosophy is to determine how you plan to control an opponent's run game with your front 6/7; and from it, whether to employ a 1 or 2 gap front. Essentially, a 1 gap defense asks its linemen to attack his assigned gap with backfield penetration, while a 2 gap team asks its linemen to control the gaps on either side of a blocker through the occupation of said blocker.

Odd tech or even tech is not indicative of a specific gap philosophy; modern defenses often use line stunts in which linemen slant towards a different gap or blocker from where they lined up at the snap. For example: if a 1 gap team is in 4-3 Even (2 tech DTs), they will stunt into gaps at the snap.

Conventionally, 4-3 teams are 1 gap and prefer quicker linemen to wreak havoc; while 3-4 teams are 2 gap and want immovable linemen to keep blockers off the linebackers, but this is not necessarily the rule -- you can run a 2 gap system out of the 3-4. A handful of innovative teams like the New England Patriots and Seattle Seahawks have begun to combine the two with a 4-3, 1 gap alignment on one half of the field and a 3-4, 2 gap alignment on the other.

I included diagrams below for each gap philosophy to help you visualize the difference. The first image diagrams a 1 gap 4-3 Over. The second diagram showcases a 2 gap 3-4 Even. Notice that the 1 gap defense asks its linemen to shoot a gap, which obviously lends itself to aggressive line play. Meanwhile, the 2 gap linemen must control the gaps on either side of the blockers across from them to clog run lanes and protect their linebackers.

1 gap
2 gap

Images courtesy of

Since Clemson thrives in Brent Venables' 1 gap system, it is where our focus shall remain. 1 gap is considerably more aggressive in part because it asks its linebackers to help control the line of scrimmage through a specific gap assignment (you'll see plenty of fire and bullet blitzes in which linebackers look to shoot the gap or at least clog it), but mainly because it asks its defensive linemen to attack the opponent's backfield and make plays themselves, rather than occupy space to keep the linebackers free.

4-3 over bubbles

The diagram above illustrates each member of the front 7's gap assignment in a 4-3 Over front. Notice the linebackers are responsible for the "bubbles" (holes) left uncovered by the alignment of the front. In modern college football with the prevalence of the spread offense, many Sams (strong side linebackers) are replaced in favor of a nickel corner outside. Or, the defense can keep the Sam on the field and split him wide in coverage. Gap responsibilities vary by personnel and play call, but the point is that all gaps can still be filled no matter the personnel.

4-3 Over Front

The 4-3 Over largely began at Oklahoma State under defensive coordinator Jimmy Johnson, who sought a remedy for Oklahoma's powerful wishbone teams. But it was while he was the head coach at Miami that Johnson evolved the front with speedy DEs and OLBs to effectively rid the wishbone's reign in college football -- which ruled the sport until this time in the early 80's.

Today, the Over front is common against spread teams when a defense has a hybrid Sam (like Travis Blanks) who possesses the flexibility to cover the slot or sit in the box; this necessitates less frequent personnel changes such as replacing the Sam with a nickel corner. Even when in the nickel, Clemson's front 6 usually aligns in the the Over.

Obviously you begin with your 4 defensive linemen, but the defining feature is that the entire line is shifted to the strong side (hence the term Over). On the strong side, you will find the SDE in a 9 tech (outside the TE) and a 3 tech DT. On the weak side, a 1 tech DT and the WDE in a 5 tech. See the diagram below to visualize the alignment:

4-3 Over

On the weak side the WDE (5 in the diagram above) has the C gap, the Will (weak side linebacker) the B gap, and the 1 tech takes the A gap. On the strong side, the Mike (middle linebacker) has the A gap, 3 tech DT the B gap, and the Sam takes the C. The SDE (9) will "set the edge" and pinch the D gap outside the TE.

Again, personnel changes may alter gap assignments, and in the I-formation shown above there is actually another gap created by the fullback. This extra gap is filled by a safety, one of whom always has a gap responsibility in a 1 gap scheme; this is why Venables prefers big, aggressive safeties (more on this in a later entry).

Notre Dame's OL Obliterated

Now the practical applications: I want to showcase the night we started to believe -- not just believe, but see -- this brand new defensive line could be elite. The contests against Wofford and App State showed us little more than overmatched opponents, and the success against a horrible Louisville offensive line wasn't cause for much more than cautious optimism. Enter Notre Dame's offensive line, considered at the time to be the best unit in the country. Clemson's defensive front owned the night from its preferred 4-3 Over front.

Below, we see Venables' adherence to an attacking 1 gap philosophy where Clemson's front established its dominance in the 4-3 Over early against Notre Dame. Remember that in the Over, the 1 tech DT is on the weak side and the 3 tech DT is on the strong side; so we know this is an Over front as opposed to Even (in which the DTs align in 2 tech) or Under (in which the line shifts to the weak side and brings the Sam down on the line to create a 5-2 look). See each lineman is aligned in his gap, with Ben Boulware and B.J. Goodson in position over their bubbles: the weak side B gap and strong side A gap, respectively.

over vs ND capture

Notre Dame runs a counter (pulling the back side RT and TE) but penetration from 1 tech Scott Pagano and Boulware in the weak side A and B gaps blow it up 5 yards deep. This is the 1 gap aggression I alluded to: linemen shooting gaps and a linebacker blitzing his; quite effectively so.

1 gap vs ND

While Kevin Dodd makes first contact from the back side, it is Boulware who stops this play dead -- he shoots the B gap and gets his shoulders past elite ND left tackle Ronnie Stanley, whose zone block was merely a hold with Boulware in the backfield so quickly. Shaq Lawson stuffs the pulling right tackle to set the edge and make contact for good measure. This is the aggression and havoc on which 1 gap technique is predicated, made deadly through sound run fits and a well-timed run blitz.

In a torrential downpour against a young quarterback, Clemson was determined to take away the Irish run game. To put it mildly, the Tigers' run defense was wildly successful. Notre Dame's zone blocking could not negate Clemson's disruptive front and generate an interior push even through double-teaming the defensive tackles.

What Notre Dame had to do here was technically devote 2 blockers to 1 gap -- and they did so to both DTs in the gif below. Even when double teamed, Carlos Watkins and Christian Wilkins clogged the gaps and kept the offensive line from moving to the second level. Thus, Boulware and TJ Green were free to stuff the run in the backfield. This doesn't mean Clemson suddenly played 2 gap technique; it was dominant, aggressive, gap-shooting line play and ND's offensive line was overwhelmed:

ND stuffed

Here's a sideline angle of an Over front, but this time against the pass. On the strong side, Lawson is in the 9 tech outside the tight end and next to him is Watkins in 3 tech. On the weak side, Wilkins is in 1 tech (war daddy) and Dodd in 5 tech outside the right tackle.

side angle over front

It is Wilkins who finishes the sack, but he can ultimately thank Watkins for it. Watkins explodes from the 3 tech (exactly what you want from a 1 gap 3 tech, by the way) and collapses the pocket from the middle. From there, Lawson bullies Stanley again to keep DeShone Kizer from rolling outside, and Wilkins is there to clean up.

over front sack

Oh, and guess which front Clemson employed on the game-winning stop? The 4-3 Over:

ND 2 point stuff

Dodd sets the edge from the 9 tech and closes the D gap, which forces Kizer inside. Watkins is double-teamed from the 3 tech but forces the blockers into a pinched Kizer anyway, perhaps the play of his life and one for which Clemson fans should never forget him. Boulware flies into his run fit and stuffs the lead block in the B gap. From there Watkins need only finish what he began. Game Over.