Willie Martinez's windblown plastic bag defense is no more. In its place is Todd Grantham, freshly departed from the land of milk, honey, and growth supplements - well, strictly speaking Cleveland doesn't really have much in the way of milk or honey, but they do have an NFL franchise. So hey, good for them.
For Georgia, the results have been spotty. So far Grantham's outfit seems to be only half-effective; on aggregate they've been all right - just slightly below average against the run and pass among SEC outfits - but it hasn't been consistently slightly below average. They've spiced it up a bit, having half the unit implode most weeks. South Carolina was the run defense cratering, then the secondary did their best mid-80s Eastern European soccer stadium impersonation against Arkansas, and the run defense got nailed again against Colorado. The fascinating part of this is that the other facet of the defense was fine in all those games (165 yards passing against USC, 53 yards rushing against Arkansas, 158 passing yards against Colorado). The one exception to this trend was the performance against Mississippi State, which was more generally useless offense all around.
Although there's a good argument to be made the aggregate isn't too different from Martinez's mystery defenses, Georgia has some mitigating factors here. The first is simply personnel turnover (which we ought to understand better than most right now), but it's likely equally to do with a shift from the 4 lineman-base Martinez used to the 3-4 Grantham prefers. However, even as a 3-4 it does some things differently. This is a new defense that we're seeing, but fortunately this is still a new defense for Georgia, too.
The Basics: Line Assignments and Notation
Before we get into what a 3-4 is and how it operates, let's have a quick primer and review some notational stuff. But first, pictures!
There are two relevant pieces of information above - the letters between the guys on the offensive line and the numbers right above the line. The letters are what we can call gap designators; basically, if I show you the above diagram and ask you to point toward the weakside A gap, you're going to point at the gap between the left guard and the center (which is helpfully labeled "A"). If I ask you to identify the strongside B gap, you're going to point to the gap between the right guard and right tackle. (We're going to add another dimension to this in a bit.)
As for the numbers, they typically refer to where defensive linemen line up pre-snap. Basically, they'll put their hand down in one of the numbered spots. When they do that, we can call them "x-tech" linemen. In other words, if a defensive lineman lines up to the outside eye of the right tackle, he's a 5-tech defensive end. If another lineman lines up over the left guard's inside eye, he's a 2-tech defensive tackle. (And yes, if you have guys match those guys you have something that look a lot like a typical four-lineman setup.)
For both gaps and technique locations, the numbering / lettering convention extends past what the above graphic illustrates (i.e., if someone was to line up to the outside end of the TE, then he'd be a 7-tech: if two TEs were on the same side, the gap between them would be the D gap). Typically those are either unbalanced lines or 2-TE formations, both of which we'll come back to.
Typical Two-Gap NTs in the 3-4
3-4 refers to the number of defensive linemen (3) and the number of linebackers (4). It's designed to operate a bit differently than what we typically think of with a four-lineman defense. With a 4-3, there's strong coverage of the offensive line and it's relatively easy to obtain overloads at places. With the 3-4, it's less about overload on the defensive line and more about containment, especially with the nose tackle. The NT is key to the success of a 3-4, and he does it by trying to be a sponge.
This is typically called a two-gap NT approach. The idea here is that the NT will bull-rush the center once it's snapped, driving him back and thus threatening the A gap on both sides of the line. As a response, the offensive line has to double-team the NT to knock him out of the play and control the line. Still, the damage is done; by absorbing two blockers and keeping them occupied, that frees up the MLBs behind the NT (helpfully labeled "M" this week instead of their usual "B") to flow through the holes the nose opened up. Typically this means most nose tackles don't end up making a ton of tackles, but they generally do a good job of screwing things up enough for the offense. Based on where the NT is attacking, it's easy to bring "overload" pressure behind the NT; in the above picture, any of the four backers can also blitz, but the MLBs can get a numbers advantage on the side the double team comes from.
Terrence Cody is a classic example of a Big Body Presence (tm Pierre McGuire); he does a great job of getting in the way and making things difficult. He's also big; he has a lot of meat that needs to be shoved out of the way, so he constantly commands double-teams. Even with that, it's possible to consistently beat double-teams if your NT is just straight-up insane, even if he takes a two-gap approach. However, those guys are generally the exception rather than the rule. More importantly, they're coached differently.
As an aside, Ndamukong Suh is likely the first name that pops to mind when talking about dominant nose players - and he is. However, Bo Pelini doesn't use much 3-4; he instead uses an unbalanced defensive line, which is a bit unique. The NT typically sits as a 1-tech, but the rest of the defensive line sets up like a 4-3. (As a homework assignment, go through that Brophy post and identify all gaps and initial locations. First person to comment with all the correct notations gets to play the Suh position for us against Memphis.)
As for the other roles: they do change somewhat, but I'm electing to not address that here. Basically, moving to a 3-4 gives you more speed than you'd typically have in a 4-3, and the roles are basically answers to the question "what do we do with this increased speed?". The DEs are typically either 3-tech or 4-tech. The MLBs are typically somewhere between the NT and the DE alignment, and the OLBs are typically hanging out around the outside of the tackles (somewhere around a 6-tech or 7-tech).
Todd Grantham and One-Gap Nose Tackle in the 3-4
Pelini's 4-3 nose approach is similar to Grantham's 3-4 nose approach. In Pelini's scheme, the NT isn't a typical two-gap player; he's a DT lined up as a 1-tech instead of a 2-tech or a 3-tech. As a result, the NT doesn't have to be a two-gap player. Instead, he gets to challenge a single gap, which allows him to get more consistent penetration and generally cause havoc. That's the theory behind Grantham's take on the 3-4:
Note that the NT in this formation doesn't actually line up as a 0-tech; he's instead slightly offset at the strongside 1-tech. (He doesn't necessarily have to be there, but it's easier for illustrative purposes.) Because he's moved directly off center, he can easier challenge a single gap instead of the typical two-gap approach, meaning he'd go to either the left or right of center instead of right at him. That in turn forces the offense to respond differently than they would against a two-gap NT, and it's similar to how an offensive line copes with a DT in a 4-3. In addition, shifting the NT to a 1-tech in essence forces the side that needs to double. Because the NT in the example above is shifted slightly, the left guard and center have to combine on the block (the right guard will never make it over there), and good things happen.
What kind of good things happen? Instead of being reliant on your NT soaking up two interior linemen, he directly threatens a gap, which in turn forces a hard response from the offensive line. The defensive end keeps the other guy on the line occupied, and the MLB on that side doesn't have to deal with any blockers. That means the MLB coming in gets to clean up the mess, and if he doesn't, then the OLB on that side gets to.
There's more than just that, though. Shifting the NT to single-gap allows you to do things like stunts, full-side overload blitzes (for example, in the above diagram the TE cannot release into his route if it's a pass play, otherwise it's four blitzers vs. three linemen and the QB gets peeled off the turf; If it's a run, all blockers are accounted for and the playside safety can easily snuff it out).
It's a Numbers Game, Silly
For the offense, facing a 3-4 is a little scary, as it's easier to apply overload to points on the line and bring pressure from all points. Similarly, it's easy to apply four-underneath coverage (under a cover 2 shell), which makes it formidable against the pass. The additional LB gives it a bit more speed, too. However, it's also vulnerable at points a 4-3 isn't. For example, the formation below is pretty tricky to deal with:
In the above shot, we've now added D and E gaps on the left side of the line, which puts the typical 3-4 front under pressure from points it's not familiar with. As long as the defense sticks with a 3-4 (and doesn't put a backer with his hand down to the outside of the LT in the C gap), the offense has a numbers advantage thanks to a personnel advantage. That sounds weird (isn't that 7-on-7?), but look at the left side of the line. We have a 5v4 advantage there (6v5 if we include the WR on the outside), which negates the 4v3 advantage the defense has on the weakside of the formation. It'll be the responsibility of the weakside MLB to get across the formation to the point of attack, but in the time he takes to navigate existing blocks, the RB may easily pass him.
If we wanted to make this even meaner, we'd switch the interior TE with, say, the right tackle - this puts the right side of our line in a bit of danger if the RE can get past their blockers, but there's a lot of beef on the left side.
The most natural response to this kind of formation (whether balanced or unbalanced) is:
This partially negates the rushing advantage we had before, but there's now a passing advantage on the strong side of the formation (especially if we leak the RB out on a screen or some such. This is a "safe" response by the defense, but they can attempt to lock out the strong side entirely. They can do this a couple of different ways, but I'll only show one.
Again, we have a numbers advantage here, but it's on the weakside of the formation now. We also have a slight coverage advantage, as we've forced a defense designed to operate mostly in Cover 2 to move to a 1-high look (which is something they're not as familiar with) - more importantly, the Z receiver and the RB can work the CB (especially if the X receiver challenges the defense over the top). The corners here are in real danger of both being drawn out of position, at which point weakside swing passes are a real danger - and a real opportunity.
This is just one way to develop a numbers advantage against a 3-4, but there are other ways. (Power plays, which pull the non-playside guard across the formation as an extra blocker, are another cheap and easy way of attacking gap mismatches and getting a numbers advantage. Replacing a TE with a FB and running to the weakside of the formation also works.) Basically, the games that we can play against a typical 4-lineman defense are similar to the games we can play against a 3-4, but we have to contend with a bit more speed at the expense of a little bit of a loss in size. For us right now, that's a net positive; we're not running anything close to a complex offense and the personnel sets we can use to exploit a 4-3 type defense are a bit different than the sets we can use against a 3-4. Fortunately, the 3-4 exploiting sets match better with our offense and our desired personnel.
This should be a much easier week to get a numbers advantage against a defense. That in turns means success through both the air and ground. And if you have a wrecking ball of a RB, then so much the better. That's where Tauren Poole comes into play (and to a lesser extent, David Oku). If this defense is put into awkward positions and additional gaps to account for, that will open up holes elsewhere. No reason to not take advantage of that, right? Matt Simms should be capable of challenging this secondary enough to keep them honest. Then again, we were just hoping that with Crompton last year; if the Bulldog Random Stopping Coin turns up good rush D, Simms can do his best Crompton-turned-Manning impersonation, too. Either way, this should be fun.
The Power causes problems against a 3-4. (That link also has a larger category on 3-4 defenses that will help outline a little bit more.)