TENDENCIES: 2024 First-Half Defense

A big-picture view of what Nebraska's defense has run in the first six games of the season and how effective it's been

Oct 15, 2024

Marques Buford Jr. breaks up a pass against UTEP. Nebraska’s corners have played press coverage at a 17% higher rate this season than in 2023. Photo courtesy Nebraska Athletics.

Bye weeks are times when most football teams will do a thorough “self scout,” a deep examination of how their squad has played, through both film and data. With so much of each game week spent on prepping for an opponent, there’s little time to reflect on what your own team is doing. The bye offers a chance to step back and take a big-picture look at yourself.

Coaches will take on the mantle of approaching their own team’s profile like an opposing staff would when preparing for a game, looking for both strengths they should be leveraging more often and weaknesses other teams are trying to exploit. A lot of that work happens in the film room: Do we need to tweak how we run Counter? Do we have a tell in our secondary’s alignment that’s allowing opponents to know when we’re about to run Cover 2? Things like that. But with advanced stats playing an increasingly important role in the sport, that’s factoring in more and more now, too.

I like to do a similar big-picture look at the bye week; I think it’s a useful exercise to examine an overall picture of where each Nebraska team is at, how it’s operating, and how much success it’s having. I chart dozens of elements on both offense and defense from each game, from personnel usage, to alignment, to play concepts. I also chart how often those elements are “successful” under success rate, a common efficiency metric. I collate all that data each week in a massive Google Sheet, and it spits out an overview of, essentially, how often that element is being used and how often it’s working. I also like to compare that data to past seasons, so that we can see what’s changed, in both the operation and efficiency.

That’s what this post will dig into. This iteration will focus on the defense, and I’ll have the same exercise for the offense out later this week. I’ll also do this same thing for the offense and defense at the end of the year, so that we can see what changed in the second half of the season.

As a brief explainer, it looks like this:

This is just one example from later in the post. The first two columns on the left in black and grey are the data from last season, with the black the usage rate (how often Nebraska is using said element) and the grey the success rate (how often said element is working). The two columns on the right in red and lighter red are the data from this year, with the dark red the usage rate and the lighter red the success rate. So, to be specific for the graphic above, the black column tells you how often NU used each type of rush in 2023, the gray column tells you how effective each type of rush was in 2023, the red column tells you how often NU used each type of rush this season, and the light-red column tells you how effective each type of rush has been this season.

I’ve broken it out into several sections for us to examine for the defense:

General Performance
Personnel/Play-Type Defense
Fronts
Boxes
General Rush
Blizes/Pressures
Coverage
Safety Alignment
Press Rates
Coverage Rotation

Let’s get started:

General Performance

For all of the fan/media concern about the defense after the Northern Iowa-Illinois stretch of games, virtually all of the advanced statistics and efficiencies would say the Blackshirts are playing better than last year’s group midway through the 2024 season.

SP+ views Nebraska as having the best defense in the country (!!),1 six spots higher than it finished in 2023. Compared to last year, the 2024 defense so far has a higher overall success rate, is allowing opponents fewer big plays, is generating more big plays of its own, has been better on all four downs, has improved in passing situations, and is forcing opponents into longer third down attempts. The improvements aren’t by huge margins, but considering most people figured these numbers would take a step back, it’s hard to complain about slight improvement across the board.

The one area that’s been an issue relative to last year has been in short yardage, but even that is a little less concerning when you dig in to it: NU has only gotten stops on 40% of its third and fourth downs of 3 yards or shorter, an 11-percentage-point decrease from last season. But that figure being low is largely a result of the D going 1-for-10 combined in those situations in those Northern Iowa and Illinois games. In the other four contests, they were 9-for-16, or 60%. Outside of those two games, it hasn’t been an issue.

The one caveat here is the schedule. FEI ranks the offensive schedule Nebraska has faced so far at 107th nationally. And more challenging offensive units are coming down the pipe: Both Ohio State and Southern Cal have top 10 SP+ Offensive Ratings, and Indiana is in the top 15. Even teams like Wisconsin and Iowa with poor/mid ratings have strong running games. Things like SP+ and FEI do adjust for a team’s schedule (meaning they’re evaluating if you’re beating the bad competition you’re facing thoroughly enough to justify your ranking) but the success rates I track are just raw totals. Those will likely fall as NU plays better offensive attacks.

Personnel/Play-Type Defense

I talked a little bit about this in last week’s post, but coordinator Tony White has shown more personnel flexibility this year than he did last season. Nebraska’s “base” defense is already what most teams would consider to be a nickel personnel (meaning five defensive backs on the field), and last year White pretty much exclusively used that base nickel look, with two defensive tackles, two edge rushers, two true linebackers, two corners, and three safeties.

The rate of the base nickel usage has still been high, but it’s fallen about 19 percentage points in 2024, going down to 74.1%. In its place, NU has nearly tripled its usage of a “pass rush” personnel, in which it takes one of the defensive tackles off the field to bring on a third edge rusher, and greatly increased its use of a “heavy” personnel, taking an edge rusher off the field to bring on a third defensive tackle. It’s also even run some “dime” personnel — taking one of its linebackers off the field to bring on a sixth DB — on 2.7% of its plays, something it didn’t do at all last season. All eight of those dime snaps came against the high-flying Colorado offense, so that hasn’t been a consistent thing.2 But it has happened.

It’s also worth noting how good the pass rush groups and dime looks have been. There’s some noise there, as they’ve both largely been employed in longer down and distances and third downs, so those are tough situations offenses are unlikely to convert already. But for those rates to be 87.5% and 75.0% is pretty dominant, regardless.

In terms of how Nebraska has defended specific types of plays, NU has, essentially, gotten very slightly worse against the run but seen a big improvement against the pass. Nebraska was able to field an elite D last year despite being pretty leaky against true passes, fielding a success rate just over 60% and giving up a lot of chunk gains. That’s improved significantly in the early going of this year, with the success rate up over 9 percentage points against true passes. That’s partially due to NU playing a lot more Cover 2 and two-high safety looks, something I’ve talked about in previous posts and will come up later when we get to the coverage and safety data. But, this is some evidence the move to the two-high structures by White is paying off against the pass.

The eye test would say NU has been worse against the run in 2024 than in 2023, but the success rate against true runs — designed handoffs by the offense — is only down about 2 percentage points. The real culprit has been run-pass options, commonly called RPOs. RPOs have been a bugaboo in the first 18 games of Nebraska’s use of the 3-3-5, with the optionality of the plays presenting answers for offenses to the scheme’s amoeba nature. NU is at just a 50% success rate when defending RPOs, a big discrepancy in their performance against true runs or passes. In sort of an idiosyncratic turn, this light-box defense has actually been more effective at defending old-school teams with designated run or pass plays than it has the more modern concepts. Illinois, in particular, killed NU with RPOs, with a 65% success rate against NU on its 23 RPO attempts, nearly a third of its snaps.

Four teams — Indiana, Ohio State, USC, and Wisconsin3 — on the back half of the schedule will significantly use RPOs.USC, in particular, will use them heavily. If you want an under-discussed factor that could determine the results of the second half of the season, here’s your flashing red light.

Fronts

Another big change we’ve seen related to the two-high coverages is the near elimination of the five-player fronts from the defense. White used those Bear fronts — with NU’s defensive line occupying the offensive guards and center and NU’s Jack and Mike linebackers aligned over the offensive tackles to create a five-player surface — on about 20% of Nebraska’s standard down snaps last year, and has used them under 5% of the time this year. It’s just hard to get to Cover 2 when you have five players on the line.

That has led to about an equal growth in the rate of three- and four-player fronts, as White has utilized fewer bodies on the line to stop the run or rush the passer than he did last season. The three-player Odd and Tite fronts have been especially effective, with a combined 68% success rate on the year. One thing to watch is that the Bear front had only been used for three snaps entering the Rutgers game but saw nine snaps against the Scarlet Knights, so more utilization may be coming.

The other notable piece of data here is Nebraska’s pressure package looks putting up a 79.5% success rate. “Pressure packages” are the designer alignments defensive coordinators cook up for passing situations. In these pressure packages, NU will often sub on James Williams and Princewill Umanmielen, as well. Like with the pass rush personnel, these are usually being used in long down-and-distance situations that are already difficult for offenses to convert, so the success rate for defenses in these situations is going to naturally be higher. But NU’s increased its success rate in these looks from last season by 17 percentage points. Insane improvement.

Boxes

Keeping with the lighter front data, we can also see NU through the first half of the year has greatly decreased the amount of people it’s playing in the box. I define a light box as any alignment in which the defense has one fewer defender inside the tackle box within five yards of the line of scrimmage than the offense has blockers, a standard box as any time the numbers match in that space, and a heavy box as any time the defense outnumbers the offense.

I think this data is slightly skewed by a game against UTEP against a goofy offensive system in which Nebraska played with a light box on 86% of its snaps (four of the other five games were in the 35% range) but 35% is still a high rate of operating a player down, and NU has also lightened how it plays even by the eye test. Against an offense in 11 personnel with an attached tight end (so six blockers: the five offensive linemen and the tight end), Nebraska has predominantly been playing with just either four down linemen and one linebacker or three defensive linemen and two linebackers within the frame. These light pre-snap looks often turn into standard boxes after the snap when a safety rolls down or overhang linebacker fills, but pre-snap NU has been decidedly playing with fewer bodies near the line of scrimmage.

You can also see than in the four-, five- and six-player raw box totals comprising over 85% of their plays.4

General Rush

Nebraska’s ability to win more often with a four-player rush was a big talking point in the offseason, as White frequently had to blitz or bring extra rushers in 2023 to generate pressure.

There’s some conflicting data in whether that’s working. This is the first point: Through six games, NU has relied on the four-player rush more often — increasing its usage by over 15 percentage points — but it has only been marginally more effective, increasing in success rate by only about 1 percentage point.

The rate of the three-player rushes has remained nearly identical, so that increase in the four-player rush has come almost totally at the expense of the five-player rush plays — remember, less Bear front usage, too — and bigger blitz plays with six or seven rushers. Nebraska’s rate of five-player rush plays has dropped by a third, and its rate of six-player rushes has been cut in half. Both of the five- and six-player rush looks have retained their effectiveness, with the six-player rush plays actually delivering stops more often than it did last season.

Thanks for reading Black 41 Flash Reverse! This post is public so feel free to share it.

Also notable here is how effective plays with a stunt — when the defensive linemen switch gaps or try to set “picks” to spring a rusher free — have been. Those total plays with stunts have an 81% success rate, and plays with a T/T stunt — meaning the two defensive tackles are operating the stunt — have yet to deliver an unsuccessful play in 11 uses this season. That’s largely a credit to how good Ty Robinson and Nash Hutmacher are.

Blizes/Pressures

Here’s the second point on the four-player rush: While White is using the four-player rush more often, he’s still blitzing at about the same rate.

How does that make sense? That’s because an increased portion of NU’s blitzes so far this season have ended up bringing just four rushers. They’ve largely accomplished that either by lining up with three-player fronts and bringing a fourth rusher (technically a blitz) or by giving the appearance of bringing a five-player blitz and only rushing four, as a defender on the line drops out.

So you can sort of make both points: White has been able to rely on the four-player rush more often, but it’s also not really been through just lining up four players on the line and letting them work one-on-one — it’s still necessitated a high blitz rate.

There’s one other piece of data that does support the four-player rush being better: NU’s plays without a blitz have been over 5 percentage points better in success rate this year. Last year, Nebraska’s plays with a blitz on were 7 percentage points better than non-blitzes; this year, the blitzes are almost 3 percentage points worse than the non-blitzes. “Plays without a blitz” would also cover three-player rushes out of three-player fronts and five-player rushes out of five-player fronts, so it’s not strictly a measure of the four-player rush. But NU’s standard rush has improved.

One other change to clock here is where NU’s blitzes are occurring on the offense. Last year, NU blitzed an A gap (between the center and offensive guard) on 20% of its total snaps, and blitzed a C gap (between the offensive tackle and tight end) on about 19%. This year, it’s been a more even spread between the A gap, B gap (between the offensive guard and offensive tackle), and C gap, with the three at 13.6%, 16.9%, and 14.0%, respectively. Although this could be heavily influenced by individual game matchups, and I want to see a whole season before I draw any real conclusions. Something to watch.

Coverage

Here’s the biggest change to the defense: Nebraska has become a Cover 2 team.

NU spent last season playing Cover 2 on just 11.9% of its snaps, playing Cover 3 and Cover 1 combined on over two-thirds of its plays per my charting.

But this year, the Cover 2 rate has tripled, with the coverage becoming Nebraska’s most used at 35.3%, 13 percentage points higher than any other coverage. It’s also been wildly effective, with a 70.6% success rate, a better success rate than any other coverage NU ran last year.

NU has specifically been running a lot of a version of Cover 2 called Tampa 2, which puts a player covering vertically up the middle of the field, so that the defense often ends up with a post safety and the coverage plays out more like Cover 3. Tampa 2 has been a popular coverage for 3-3-5 defenses in the past, dating back to the original 3-3-5 with Rocky Long at New Mexico — Brian Urlacher was often that “pole runner” playing the middle of the field deep — but it sort of went out of vogue across football in the 2010s. But it’s made a recent resurgence around 2018 thanks to John Heackock’s 3-3-5 scheme at Iowa State and was used by Matt Rhule and Phil Snow at Baylor around that time. It looks like Nebraska has joined in on that Tampa 2 wave now, too.

Also notable is how much less man coverage in general NU is now playing. Nebraska was in man on about 43.2% of snaps last year, but this year has only spent 27% of its snaps in man. The performance in man didn’t really dip, but NU did get slightly better at at executing zone coverages and has been using more zone, on about three-quarters of its snaps.

Per my eye, Marques Buford Jr. has struggled a bit more in man but been good in zone — which also lets him use his physicality well against the run — so that could be one reason behind the increase in zone use. But both Tommi Hill and Ceyair Wright are good man coverage players, and with Wright seeming to be in line to start over the back half of the season and Hill returning from injury, we could see more man in the next six games.

Safety Alignment

As more two-high coverages have been used, we’ve seen a corresponding increase in how often NU is playing with both two and three safeties lined up deep before the snap. Its rates of two-high and three-high pre-snap alignments have each gone up over 10 percentage points, with two-high now constituting 39.5% of all plays and its rate of three-high almost doubling to 21.3%.

Give a gift subscription

All three main safety alignments — single-high, two-high, and three-high — have all been very effective with over 64% success rates, with single-high actually performing slightly better than the other two. Single-high is still being used on over a third of NU’s plays, so it’s still getting plenty of run; it’s just not being used on over half of Nebraska’s snaps in the extreme way it was last year.

In terms of the placement of its individual players at safety, NU’s most common pre-snap alignment has been with the Rover (Isaac Gifford) and strong safety (DeShon Singleton) lined up deep over the top, and the Nickel (Malcolm Hartzog Jr.) down near the line of scrimmage, with that look constituting nearly a third of its snaps. But it’s also played a lot with the looks of Gifford deep and Singleton and Hartzog down (24% of snaps), all three safeties deep (21.3%), and Singleton deep with Gifford and Hartzog down (10%). All of these looks have been effective.

On whole, Gifford has lined up deep on nearly 80% of his snaps, though he often ends up rotating down into the box at the 10-12 yard depth, either as the pole runner in Nebraska’s Tampa 2 coverages or as a robber zone coverage player in Cover 3. In the reverse, Hartzog has spent nearly 70% of his snaps near the line of scrimmage.

Press Coverage

One other secondary change is that NU has been playing more press coverage, where corners play tight to the line of scrimmage and challenge receivers physically off the ball instead of allowing free releases. NU’s plays with any press coverage are up to 55% from 34% last season. Though I didn’t chart the press plays by position last year, so I don’t have comparable data, a significant portion of NU’s press reps last season were with nickel Omar Brown pressing the slot. But this season, a majority of the press attempts have come from the outside corners.

That’s partially because of the increased Cover 2, as well — outside corners are responsible for the flats in Cover 2, so their coverage responsibility is near the line of scrimmage, and a deep safety over each half of the field makes a blown press attempt less costly. But they also seem to trust these outside corners to press more. The staff has deployed Wright in press on a majority of his snaps, and they also will roll Hill into press. Both are lankier players, which makes press coverage a little easier.

Buford and Hartzog — both smaller players — have been utilized in press less frequently. Hartzog in the slot has been used in press on just 10% of his total snaps.

In a bit of the coincidence, the plays with press coverage and without press coverage have an identical 63.6% success rate.

Coverage Rotation

I’ve written about this several times in the game recaps, but NU has also significantly increased the amount of plays where it rotates its coverage shortly before or just after the snap. NU was doing this disguise tactic on about 28% of its snaps last season and now uses it on nearly half its plays.

The plays where it does rotate its coverage have been about 6 percentage points better than the non-rotational plays. In the first three games of the season, NU was heavily rotating into two-high coverages, but in the games against Illinois, Purdue, and Rutgers began rotating into single-high coverages more often, with total single-high rotational rates of 20.3%, 30.9%, and 18.8% in those three games, respectively, to make the percentages even out more at midseason. NU’s rotations from two-high coverages to single-high (2 to 1 Rotation in the chart above) actually finished as its most used rotation for the first half of the season.