What Is: A Scrape Exchange

What Is: A Scrape Exchange Comment Count

Seth December 20th, 2016 at 10:24 AM

[This series is a work-in-progress glossary of football concepts we tend to talk about in Upon Further Review and Neck Sharpies, etc. Previously:

Offensive concepts: Run-pass options (RPOs), High-Low passing routes, Covered (ineligible) receivers/tight ends, Blocking: Reach Blocks, Kickout Blocks, Wham Blocks

Defensive concepts: Keeping Contain/Lane Integrity, Force Player, Hybrid Space Player, One-Gap Fronts, Coverages: Tampa 2, Pattern-Matching, Quarters and how MSU runs it

Special Teams: Spread punt vs NFL-style]


In the Iowa UFR Brian talked about how opponents had solved Michigan’s Peppers-as-Option-QB (we were calling it the “Pepcat”) package with an old fashioned zone read beater: the scrape exchange. Brian on the above:

Peppers is reading the DE and pulls; Iowa inserts a linebacker directly into his path since that DE is covering up the inside gaps the LB would usually be tasked with.

Since I watched the Rodriguez era at Michigan this is familiar to me. Also familiar to me: the various counter-punches Michigan threw at this. Remember that brief era when Carlos Brown and Brandon Minor were running directly off tackle for big chunks on the regular? That was due to Michigan's response to this kind of approach: blast that guy slanting even further inside, kick the linebacker out, and thunder directly to the secondary.

Since that was buried in a UFR I figured we might discuss scrape exchanges in some more detail here.

What’s a scrape exchange: It’s a defensive concept that flips the roles of two backside defenders, thus covering both sides of a quarterback’s zone read. The guy the offense thinks it’s optioning, usually a defensive end, “crashes” (move horizontally across the line of scrimmage) and is “exchanged” for another defender, usually a linebacker, who “scrapes” to the area the end vacated.

What’s it for? It’s the paper to the zone read’s rock. So you remember zone read:


This is the play that Rich Rodriguez invented to dawn the spread era. The offense leaves the backside defensive player unblocked and the quarterback options that guy. If the player (usually a defensive end) takes the opportunity of no blocker to scrape across to the running back’s path, the quarterback keeps it and runs into all the space left behind. If the optioned defender forms up to keep the quarterback contained, the running back gets the ball with the benefit of that extra blocker.


After decades there are lots of variations, but this is the gist of that offense. A scrape exchange makes the quarterback keep it, and makes that decision also wrong:


The quarterback running a zone read will see the defensive end crashing and keep the ball, only to find the linebacker appearing where the quarterback was about to run it. What the QB is expecting is on the left below; the result of the scrape exchange is on the right:


[After the JUMP: see it in action, and ways to beat it]


Neck Sharpies: The Don Brown Defensive Glossary: 3-4 Edition

Neck Sharpies: The Don Brown Defensive Glossary: 3-4 Edition Comment Count

Seth March 29th, 2016 at 12:00 PM


[Photo: Upchurch]

Last week we introduced the defensive terminology for Don Brown's base defense and his 4-lineman sub packages. Quick clicky-popup diagrams of the 4-3 and 4-2-5 forms we covered:


This week I'd like to get into the 3-4 and 3-3-5 and 3-2-6 looks, or in Brown's terminology, the "50" formations.



The BC defense Brown brought over is a base 4-3 and 4-2-5 nickel, and they'll run a relatively small suite of plays from that base on most downs. But a lot of the fancy stuff—truly, most of the playbook—are out of what are usually called "30" and Brown refers to as the "50" fronts*, i.e. formations with three defensive linemen.

Here's the basic version, as taken directly from the 2013 Boston College playbook that James Light posted.


Technically, the "Tackle" (Hurst's position) has been replaced with a "Backer" (B). When you hear about a guy you thought was playing defensive end being called a "linebacker" (e.g. Kemp) it's possible he's playing the Backer position. If a dude's getting mentions as an "OLB" that's also a sign they're using him in that Backer/Sam role, where "Sam" means "Jake Ryan-esque."

That isn't anybody yet—I've been using Winovich as a placeholder—but the ideal here is clearly LaMarr Woodley: a 6'2/260-ish, athletic, stand-up, high-burst, space-tackling, strong-enough-to-stand-up-to-blocks attacker who can play rush end or cover some. That last is notable because it gives the 50 formations a suite of tactics that are generally absent from Brown's 70 formations: zone blitzes.

* [It's 50 and not 30 because look at the pic above and count the guys on the line. Now think back to that ol' Schembechler 5-2 "angle" defense. The more things change…


[After THE JUMP: bandits, canidae, diagrams that look like they're saying "Mike Gedeon" and "Will McCray", and blitzes. Oh lawdy do we got blitzes.]


Neck Sharpies: The Don Brown Defensive Glossary: 4-3 Edition

Neck Sharpies: The Don Brown Defensive Glossary: 4-3 Edition Comment Count

Seth March 23rd, 2016 at 11:00 AM

[Huge thanks to Steve Sharik for getting a lot of this for me]


He's got nickel down. Also Sam, Rover, Money, Jaguar, Tractor, Dog, Pup, Cat, Bandit, Greyhound, and Aardvark. Read on to find out which two of those are not actually Don Brown positions that Peppers will play. [Bryan Fuller]

We had some bona fide MGoDudes attend the coaching clinic and the open practice in Florida, and they've reported back with a wealth of information about the new Michigan defense.

Coach Steve Sharik is writing up a full feature on it for HTTV, and in the course of editing that we went through all of the standard (and some of the non-standard) positions and terminology. I thought that would be extremely valuable to those of us trying to parse the coachspeak all spring, and figure out exactly what position various Guys and Dudes and whatnot are playing.

This week I thought I'd tackle the 4-man fronts that Michigan will run as their base defense. Brown also has myriad 3-man fronts (whence Winovich) that I'll get into next week.

Here are the two basic 4-man, or as Brown calls 'em, "70" fronts: 71 and 72.


These two alignments we'll see most of the time on standard downs, with personnel changing based on what the offense has in there. If you didn't spot the difference between 71 and 72, it's how the nose and end are aligned. In the first the nose is over the center (a 1-technique) and the end is in a 5-technique off the weakside OT. In 72 those guys have shifted over some, putting the nose over the guard (2-technique) so the end can split out wider. The first is stronger against inside runs, the second gives the end an easier path to pass rush or play a zone read.

And here are the base positions:


Let's meet them.

[After the jump: What's an "A", what's the difference between a Sam, a Jaguar, and a Money, and what the hell is Peppers?]


Neck Sharpies: Not Getting Even

Neck Sharpies: Not Getting Even Comment Count

Seth December 2nd, 2015 at 10:11 AM


This would not go over well.

After the injury to Ryan Glasgow Michigan has struggled to stop zone running. Indiana and Penn State tore the defense to shreds on stretch or outside zone, until Penn State decided the thing that got them two huge gains in three attempts wasn't worth using again (please keep James Franklin forever kthx). I drew that up last week and found Michigan was still trying to defend runs by shooting the DL upfield and dominating one-on-one matchups up front, as opposed to soundly preventing guards from releasing onto the linebackers.

With Urban Meyer, one of a few true masters of modern running attacks, doing the planning for the Game, we knew Michigan's defensive coaches would have to pull something out of our butts to stop it. Here's what we found in our butts:

Michigan broke out a 3-3-5 defense with an "even" front. Offensive coaches have different names for fronts but the basics are:

  • Under: NT on the center, shaded to strong. DT on a guard. (aka Weak, 50)
  • Over: NT on the center, shaded to weak. DT on a guard. (aka Strong)
  • Even: DL are lined up over guards, none over the center. (aka Split)
  • Okie: Center is covered, guards are not. (aka 30)
  • Bear: Center and guards all covered. (aka 46, Eagle, Double Eagle)

These can be split into "Odd" (under/over) and "Even" (Even, Okie, Bear). It is usual for just about any defense to come out in multiple fronts over the course of a game, though Bear and Okie are more rare than the other three.


Anyway that's what that means. By putting guys over the guards it makes it tougher for them to release to the next level. Michigan State used to love their even fronts back when Bullough was their best run defender, and that tells you something about the design of this defense. Tweaking your defense is about making life hard on your better players so things are easier for the rest of your players. "Even" makes life hard on the MLB, since that center is getting a free release unto him.

There's nothing 100% unsound about this defense. Depending on the offense's play, one LB is likely to get a center on him but the other is often a free hitter. If your LB eating the block is good at beating those consistently, or your free hitter is a ninja who sniffs out the play and attacks ferociously, or your unblocked guy is coached to play aggressively against an option you can defeat a basic run play regularly.

[After the JUMP, we totally can't]


On Pattern Matching: Saban's Cover 3-Man Hybrid

On Pattern Matching: Saban's Cover 3-Man Hybrid Comment Count

Seth April 29th, 2015 at 9:43 AM

Next time you see this you'll know what's going on

In previous layman's discussions on how fancy newfangled anti-spread defenses function I've talked about how Quarters works, and how MSU used aggressive alignments with it to dominate the run game at the cost of greater risk of getting beat over the top. Each time I alluded to the fact that Saban's defense is similar in concept except where Quarters is a Cover 2/Cover 4 hybrid, Saban's is a Cover 3/Cover 1 hybrid.

We will see it this year. Every defense uses some Cover 3 and Cover 1 as a changeup, but Saban's base system, now all over the SEC, has spread into various Michigan opponents. Penn State kept it around while transitioning to Bob Shoop's version of Quarters. Maryland had it last year; not sure if their 4-3 transition includes a coverage shift. I think BYU (which is going back to 3-3-5 with Bronco Mendenhall overseeing it personally) is expected to as well. Michigan State has played with it, since it's similar to what they do normally. Anyway I thought it'd be fun to get into it now, so we'll have it to reference later.

Resources/hat tips:

  1. Rufio of Cleveland Browns SBNation blog Dawgs by Nature.
  2. Matthew Brophy's incomparable series on Alabama's D: part i, part ii, part iii, and his "Rip/Liz" video.
  3. Eleven Warriors' Kyle Jones's film study
  4. Ricky Muncie of Crimson Tide SBNation blog Roll Bama Roll
  5. Chris Brown, of course. Of course.
  6. Pre-emptive thanks to actual football coaches who post in the comments and point out where I got something wrong or over-simplified.

I'm Not a Coach Disclaimer

I'm not a football coach. I'm a guy on the internet who read a lot about football.

Basics of One-High Defenses

Cover 3 is probably the most basic defense in existence. It is the defense you learn on Day 1 as a high school freshman, if not before. At that level it is a "go to this spot and then find work" scheme, past that there are techniques coaches teach to cover the gaps. Here are the two basic versions that Saban uses against standard 2x2 formations:


If you picked up on the fact that "Liz" and "Rip" begin with the same letters as "left" and "right" (or you know your port and starboard colors) you have my permission to eat a cookie.

Joe Paterno used variations of this (Rip is very close to his base defense*) since the Chatelperronian, and like Neanderthal toolkits it only looks crude until you see it in the hands of a master.**

Some things to know that we'll use later:

  • The receiver numbering system is the same as in Quarters: start from the sideline and work your way in until you're at the center. It's where they are at the snap, not before, in case motion messed with that.
  • The path you take to your zone matters a great deal. Note how guys running toward their zones are actually going through weak points in the coverage. This is for "routing" purposes: if you're there a receiver can't be.

The latter is true for all zone defenses, but it's a stress point for Cover 3 because the holes in the zone are places the offense can attack either quickly (7-9 yards downfield in the seam) or easily (deep downfield once the free safety has committed). Cover 3 coaches teach defenders to be in the way so receivers have to re-route to covered places.

The tradeoff is natural coverage strength to the middle of the field, to the detriment of the flats—if you've ever watched an NFL defense that seems to constantly be tackling fullbacks squirting out of the backfield, that's why.

The problem with Cover 3 is the same problem with Cover 2: those frikkity vertical routes:



The problem remains with pretty much any set of routes that stem from a vertical release.

The old-fashioned answer to this is play more man defense, and certainly Cover 1 (example diagram) is a complementary coverage to any Cover 3 team. In Cov1, aka "Man Free" defense, corners stay on the receivers, the erstwhile "curl/flat" guys stay on the #2's, and the middle linebacker over the RB takes the RB.

But if you're playing man-to-man defense, you'd better have men who can win their battles 97%+ of the time against theirs. If you need to activate that free safety to double up a dangerman, now you're giving up "front"—how many defenders are participating in your run fits, and once it's not an 8-man front anymore you're weak against the run. Offenses will also use rub routes, or exploit matchups, e.g. have a quick slot receiver sprint across the formation until he loses the linebacker trying to keep up.

These were problems for Saban to a much greater degree when he was dealing with the kind of talent the Cleveland Browns drafted during his DC days. By the time he got to MSU he already had his Rip and Liz and his Cov1 amalgamated into a hybrid scheme he called "pattern matching."

[After the jump]


* The Paterno-era "Hero", and "Sam" in the linked diagram were early examples of hybrid space players, and the zone-blitzing 8-man front it spawned was the basis of Rocky Long's 3-3-5 defense.

** …who discovered children were being sexually abused in his locker room and didn't tell the police because football reasons.



H4: Forty-Three Shades of Purple

H4: Forty-Three Shades of Purple Comment Count

Seth January 13th, 2015 at 10:39 AM



My biggest takeaway from last night is Michigan will need a very strong and well-coached front seven if Harbaugh is to pull a 1969 next Thanksgiving weekend.

The key to Michigan's dramatic defensive improvement in 2011 was that Brady Hoke and Greg Mattison gave Michigan's defense an identity. They went to a 4-3 under, single-gap run defense that Mattison brought from the Ravens, and over the course of the year found the best fits for the guys on hand.

Durkin knew Mattison from his Charlie Weis pants days. [photo: Joe Raymond|Freep]

You remember, despite the relative success of this transition, that some fits were more or less awkward than others. Jake Ryan was a perfect SAM. Ryan Van Bergen worked as a 3-tech or a 5-tech. Mike Martin played nose because nobody else could, and his disruption was deployed with a lot of stunts, or weird stuff like when they came up in an Okie and Martin dropped back to essentially MLB. Roh at WDE was a solid run defender but wasn't built to take advantage of that WDE-tackle matchup that's supposed to produce natural pressure.

Last year of course they went to a 4-3 over base alignment, making Jake Ryan into an awkward MLB because the alternative was Beyer as a really awkward 5-tech. The kicker: offenses were forcing Michigan to play nickel 50% to 90% of snaps, which made Ryan into either an undersized defensive end, or a guy on the sideline.

JMFR is gone but Mattison will still be around, joined by new defensive coordinator D.J. Durkin. At the Cleveland event last night I suggested Mattison’s role will be as sensei to Durkin, who hasn’t really flown solo yet (Muschamp was very involved with that defense).

It adds up to a belief that Michigan won’t change its defensive style for 2015, but what is that style? Coverages are another matter; just speaking to the front seven: should they be the under that they recruited for, or the over they transitioned to?

Refresher on 4-3 philosophy

Mattison and Durkin both coached (Durkin as a graduate assistant for one year) under Bob Davie at Notre Dame, who with Jackie Sherrill developed the Texas A&M "Wrecking Crew" defense. Jimmy Johnson (another Sherrill acolyte) took it a step further in Miami, and Pete Carroll now runs in Seattle.

You’ll note that they used different alignments. Johnson’s defenses were the genesis of the 4-3 over, and so influential that this is what people usually mean by “4-3” defense, as opposed to Tom Landry’s base version. Carroll’s been coaching the 4-3 under since he learned it directly from Monte Kiffin, who developed it at Nebraska.

The under alignment was not the base concept; the real philosophy in Kiffin's terms was to give his defensive linemen simple assignments so they could play with aggression and disruption. The benefit of one-gapping is no defensive linemen stopping to diagnose the play. Once the ball is snapped, all of these defenses want those brains thinking "go!", "put my hat in a gap," "be a factor," and "attack that block!"

Mattison used a mix in Baltimore because he had Ngata, but at Michigan he’s had an almost exclusively gap-attacking defense. The question has been what alignment to run it out of, and that’s a question of which players fit it best.

(Start at 1:17)

So which alignment is Michigan going with this year? I think again it’s a question of personnel? I make diagram.


Michigan’s short on red dudes

The above is my attempt at showing the spectrum of qualities emphasized by the front seven positions in the 4-3 over versus the 4-3 under. I also gave a small approximation of color fits for guys I know something about (Spur-like objects like Gant and Wangler left out because I ran out of colors to depict DB-ness).

It's meant to show what we mean when we talk about the why nothing's a perfect fit for the talent on hand. Suggestions for improved shading are welcome. Takeaway from this experiment: Michigan's front the next few years may be better at throwing out different looks than it will be at rotating through shark teeth.

If you trust my judgment on the shading above, the over appears to remain the best fit for the guys we have, provided they can find some backup ends (the glut of DE/DT tweeners remains). As Mattison mentioned in the video above, the half of the time you’re in nickel to counter a 3- or more-wide look, you’re in an over anyway. D.J. Durkin used a lot of smaller players and changed things up a ton at Florida, and I expect the future will be a truly multiple defense with versatile front seven players. I expect when they can’t run Ojemudia and Charlton out there at the ends, Durkin will experiment with linebacker-ish dudes out there.


Hokepoints Seeks Hope in Hazell

Hokepoints Seeks Hope in Hazell Comment Count

Seth October 21st, 2014 at 12:35 PM

I know Hoke said they spent the bye week on Michigan's "identity," by which we're pretty sure he meant scrapping any semblance of sense again in favor of slamming fullbacks into people and praying for the turnover fairy to stop hating us. But for those people actually interested in how to defeat Michigan State's lauded/loathed defense, it appears to be vulnerable when you spread 'em out and test them deep.

Quarters redux

You should remember how their thing works. The defensive backs read the inside (#2) receiver; if that guy goes vertical the DBs play cover 4; if that guy goes horizontal they play Cover 2.


Red: #2 receiver goes vertical. Blue: #2 receiver doesn't go vertical

With that many guys reading, the defense can play "9 in the box," by which they mean the safeties are part of the run fits. Their run D is gap-oriented.


Just an example. They change up who's got what

Note that screens and such are treated as runs.

[After the jump: tripping them up.]


This Week's Obsession: Over-Under on Over?

This Week's Obsession: Over-Under on Over? Comment Count

Seth June 6th, 2014 at 10:44 AM


This here Friday because not enough for Dear Diary.

What do you think of the transition to a 4-3 over? Who else is running it? Is it so much of a shift?

Ace: While I was skeptical at first—it felt like a bit like a panic move—I've started talking myself into this being a positive change. The main reason is that it should allow Michigan to generate more of a pass rush, and in less predictable ways. Seth pointed out the benefits for both Frank Clark and Brennen Beyer in his post—they slide into roles more suited to their abilities in a way that gets them on the field at the same time. Add in the ever-present threat of Jake Ryan blitzing up the middle and I think the pass-rush will be improved thanks to this switch.

When you have Clark and Beyer (and Ojemudia and Taco etc.) available this isn't the best use of Jake Ryan [Fuller]

The defense should also be better suited to go against spread attacks by keeping Ryan in the middle. He no longer has to worry about playing over slot receivers or being the primary defender against bubble screens, and when Michigan goes to a nickel, they'll most likely lift James Ross for a defensive back—adding coverage without losing much from the pass rush.

Keeping the linebackers clean against the run is also easier in a 4-3 over; Iowa's linebackers were very successful last year in part because their alignment allowed them to roam free sideline-to-sideline—I was dumb enough to confuse "DTs aren't making plays" for "DTs not doing their job" in that post, when it turned out Carl Davis and Louis Trinca-Passat were really good at holding up against double teams while the Hitchens/Morris/Kirksey trio combined for 35.5 TFLs despite rarely blitzing. I highly doubt Greg Mattison's defense will be as passive as Iowa's, but the Hawkeyes still provide a solid blueprint for how to get better production from the linebackers.

That brings me to my biggest concern, however, which is the defensive tackles. I believe the Henry/Pipkins combo will hold up fine at the nose, but the lack of experience at 3-tech is worrisome. The good news is both Chris Wormley and Matt Godin—the likely rotation there, along with Ryan Glasgow—were tweener DE/DT recruits with large frames, solid strength at the point of attack, and some concern about their edge-rushing ability; the last part matters much less now, and as long as they're not ceding ground with regularity, the experienced linebackers should be able to work behind them (Northwestern's linebackers managed to stand out in their 4-3 over even though their DTs routinely let the seas part).

My other main concern is how Ryan will handle more offensive linemen releasing to block him at the second level, but I have the feeling he'll figure it out. It's clear the coaches have been planning this shift for a while—see: Noah Furbush, MLB recruit—and despite a few minor bumps along the road I still have a great deal of trust in Mattison. If, as advertised, this shift allows the defense to be more aggressive in general and more adaptable against spread attacks specifically, I'm on board.

[Jump: Brian and BiSB go over this more. HA!]


Hokepoints Goes Over

Hokepoints Goes Over Comment Count

Seth June 3rd, 2014 at 10:35 AM

In honor of our annual right there -----> which I expect will get Kickstarted a third year in a row today, I thought I'd share a little sneak peak from it. Brian asked me to create these for the linebackers page:

4-3 Overunder

Click to big. Right-click to open in a separate window so you can reference it as you go.

That's a side by side comparison of Michigan's prohibitive starters this year before and after the "shift" to a 4-3 over and accompanying position changes were announced. Seeing it you can start to appreciate how all of those announcements make sense.

For the lay, what you're looking at are alignments of the front seven. The "under" shifts the defensive line away from the strength of the defense and the linebackers swing the opposite way to compensate. The result is very much like a 3-4 (picture the WDE in the photo above as yellow) and plays like it. In this alignment the strong side is the left because there's a TE there. Michigan would often align this to the hash rather than the offense, shifting the DL toward the sideline.

The "over" shifts the line the opposite way, but not to such an extreme. The linebackers wind up centered over the ball, and the DL spread across the formation. There is nothing 3-4 about it except the nose tackle.

Let's run through the positions to appreciate what's changed and what will be expected of them.

Weakside Defensive End (Frank Clark/Mario Ojemudia)


Ojemudia lined up as a 7-tech in the under [Fuller]

In the Under: The WDE is the leading pass rusher. He lines up so far outside of the backside offensive tackle that he'll wind up getting a 1-on-1 battle with that guy all day. The tradeoff was being further from the point of a attack in the run game. The WDE is further from the run game but in position to drop into coverage, a thing he was tasked to do quite often as the DE-like linebacker opposite him charged into the backfield. Much of the good done by the over shift is it creates double teams elsewhere to preserve the WDE's ability to attack upfield.

In the Over: The weakside end is still outside the offensive tackle, but shaded in a "5 technique," i.e. over the outside shoulder of the offensive tackle.


If you remember your 5-techs from 4-3 under school, you'll get the difference, though unlike your Ryan Van Bergens the weakside end usually doesn't have a tight end lined up to his side (ace even, H-backs and the like do happen) so he needn't be a double-team-eating anchor. The new WDE's biggest change is he's not dropping into coverage all the time. He has to control that OT in the run game, and often he has to cover the B gap. The linebackerity of the position has been removed; this man is a defensive lineman, and not necessarily a flashy one—Michigan State's been plugging their workhorse DE Marcus Rush in this spot for four years while various SDEs make the highlight reels.

The fit: Clark showed signs of being a pretty good player by the latter half of last season and now up near 260 he is large enough to not get kicked by OTs. As a pass rusher he's only like fifth or sixth in the conference, partly because the interior DL couldn't push the pocket very often, and partly because he wasn't great at closing when he beat his guy.  Ojemudia and true freshman Lawrence Marshall aren't large men in your memory, but both claim to be up to 250 now. They're all better full-time defensive ends than 3-4 OLBs.

[Jump for the rest of the DL—LBs coming up in Part II]


Hokepoints Finds Nothing in Assists

Hokepoints Finds Nothing in Assists Comment Count

Seth May 13th, 2014 at 2:00 PM


No Cam you don't get points for setting up Morgan's one-timer.

Still playing with the big spreadsheet of stats. Sometimes I glom onto something interesting and sometimes, like today, I waste a lot of time to realize a stat they track has no bearing on play at all, and then I have to write my article, and then Comcast manages to make me wish Greg Robinson was my internet provider and, well, that's my excuse.

While Ace was writing the MSU preview for this year's HTTV (you are welcome to pester Brian to start the kickstarter) I was feeding him various kill-me-now defensive stats that showed State was really good at defense last year. One thing we pulled up was a larger percentage of tackles that were assisted, something MSU seemed to share with other teams.

This does make sense if you think of plays that are good for a defense, e.g. a lot of bodies going nowhere at the point of attack, versus how long gains tend to end. Likewise you'd expect the position of the player to make a difference just because of the variance in amount of space between him and the next defender. A typical distribution of tackles was as follows:

Position Group % of Total % Solo
Defensive Line 24% 51%
Linebackers 35% 55%
Defensive Backs 41% 65%

Noise in the data: I built this from complete game stats, not play-by-play, so I couldn't separate special teams plays, etc. I did re-categorize a bunch of players listed at incorrect positions but I couldn't catch all of them. Tweener positions also throw things off: a WDE to a 4-3 under team is an outside linebacker to a 3-4 squad, 3-3-5 teams call the Spur a safety, Jake Ryan puts his hand down in the nickel, etc. There's tens of thousands of tackles in the above percentages but as we get into teams keep these inconsistencies in mind. FCS teams and stats accumulated against them were removed.

Who's doing the tackling? So in the above table defensive linemen have marginally more assisted tackles than linebackers, and both have significantly more tackles assisted than defensive backs. If tackle assists mean anything other than "more forward players are doing the tackling" we can see that by testing whether the % of tackles accrued by the front 7 or % of tackles assisted have a closer relationship to tempo-free defensive efficiency.

Tackles and assists

So yeah, it's where the tackle takes place, not some mystical ability of great defenses to get more people to arrive at the ball at the same time. And neither is that strong of a correlation. Sorry, every platitudinal defensive coach ever.

So how'd we do?

The Big Ten ranked by fewest yards ceded per play:

Team % by DL/LBs Rk % Solo Rk Def YPP
Michigan State 59% 8 48% 2 4.0
Iowa 64% 2 50% 4 4.6
Wisconsin 65% 1 63% 11 4.7
Maryland 62% 5 56% 6 5.1
Nebraska 58% 10 60% 9 5.2
Ohio State 56% 11 62% 10 5.3
Michigan 62% 4 56% 5 5.3
Penn State 60% 7 59% 7 5.3
Northwestern 61% 6 59% 8 5.5
Minnesota 54% 13 67% 13 5.7
Rutgers 63% 3 50% 3 5.7
Purdue 55% 12 71% 14 6.2
Illinois 52% 14 45% 1 6.7
Indiana 58% 9 66% 12 6.7

That Illinois and Michigan State are the top two teams at getting assists on their tackles says tackle assists aren't a thing. Rutgers was great at getting linebackers to the ball, but not until lots of yards had been accrued. Northwestern's a good study in this: in 2012 they had safety Ibraheim Campbell racking up Kovacsian solo tackle numbers, but in 2013 they had greater contributions from up front…with little increase in productivity.

I don't even see much in the way of stylistic preferences coming through. Michigan and Nebraska and Ohio State I believe (gleaned from what their coaches say at clinics mostly) are "spill" teams—they try to occupy blockers so a free hitter can make his way to the ball. Michigan State and Wisconsin and Penn State, are the ones I believe were "gap" teams—every defender has a gap he's responsible for closing.

So…okay, this stat means nothing. Good to know I guess.