Khalil Davis Earned the Opportunity to Represent Nebraska in Chicago
Photo Credit: Eric Francis

Hot Reads: A Part-Time Disruptive Defense

October 03, 2018

Is Nebraska football better than it was a year ago? Simple question and, for some, a pretty simple answer based on the Huskers' 0-4 record to start the Scott Frost era.

But football isn't simple. Take a 6-yard run on first down, for example. If you want to know more about that run than "it gained 6 yards," you are presented with countless questions. What role did the running back play? The offensive line? What about the play call? The defensive play call? Should we consider years of recruiting and available talent for each team? A straight handoff from quarterback to running back, resulting in 6 yards, contains almost endless variables.

So answering "are the Huskers' better than last year?" right now is anything but simple. It might not even be the right question, but it's one we're seeing more and more as Nebraska's current losing streak has reached eight games (dating back to 2017). That's why this week in Hot Reads I'll be looking at a different piece of evidence each day. (Part 1, Part 2)

At the end of the week, draw your own conclusions and then get ready for the new pieces of evidence to emerge against Wisconsin.

***

“In this day and age of the way your offensive football is going, the way to win games on defense is sacks, plus turnovers, minus explosive plays,” Nebraska defensive coordinator Erik Chinander said when he was hired for the same position at UCF in 2016. “We have to be aggressive, we have to take some chances.”

That's a pretty simple recipe to understand. There are just three key ingredients.

Bob Diaco's signature approach to preventing points was not so simple. He brought a perfectionist's passion and eccentricity to his "no crease" defense, an elaborately planned trap that routinely malfunctioned in its one year in Lincoln. The goal was to prevent big plays, which is a good thing to do, but it can't come at the expense of everything else. And that's not how it's meant to work, of course, but that's how it did work in 2017.

Chinander's more aggressive approach, by contrast, should've had an immediate appeal to anyone who ever has tackled or wanted to tackle anything. Go get after the ball? Great? It feels, at least to me, like a defensive version of the difference between spread and pro-style offenses. Both can work, but one often comes with aggressiveness aided by simplicity. The other is complicated and has a greater degree of difficulty (particularly at the college level).

Because Chinander's quote from two years ago is so clear, as have most of his comments been at Nebraska, it provides an easy starting point for evaluation. How are the Huskers doing in the sacks-plus-turnovers-minus-explosive plays department?

We already know the turnovers part is missing, and some of the early randomness that's involved.

But the sacks are going well. Nebraska already has 12 after four games, nearly matching last year's 14. The 2018 Huskers' sack rate (7.4%) is better than both Nebraska's (3.7%) and UCF's (5.4%) was a year ago. However, those sacks haven't quite meant as much early this season. On the Huskers' 10 drives including at least one sack, teams have scored 40 percent of the time (two field goals, two touchdowns). That's a 60-percent stop rate, which isn't bad. But you'd expect the scoring numbers to come down a bit if Nebraska keeps getting the sacks. That it hasn't early this season could be for a variety of reasons, but the biggest probably has to do with the third part of Chinander's defensive equation –– explosive plays.

In terms of frequency, Nebraska is about even with last year's defense (which, again, was willing to sacrifice some aggressiveness to prevent these explosive plays). It's not that different than 2017 UCF, either.

Percentage of… 2018 NU 2017 NU 2017 UCF
Runs gaining 10+ yards 14.4% 15.9% 14.9%
Passes gaining 15+ yards 16.0% 15.7% 15.3%
Explosive passes plus runs 15.3% 15.9% 15.1%

The difference, at least when it comes to this year's defense compared to last year's, is in the magnitude of those explosive plays. When the Huskers' defense has busted in 2018, those plays have been pretty big.

Bill Connelly's IsoPPP stat is designed to measure this type of explosiveness. If the first goal on defense is to prevent any successful plays (based on success rate), the goal when an opposing offense does run a successful play then becomes limiting the damage. IsoPPP measures the latter.

It was perhaps the one thing the Huskers' defense was good at a year ago. Nebraska gave up a ton of successful plays last year (49.9%, 129th), but those successful plays weren't huge gains. The 2017 Huskers ranked 30th in IsoPPP. (If you had to choose for a defense to be good at one of these things, you'd choose success rate, by the way.)

That equation is flipped so far in 2018. Nebraska's defensive success rate is solid (39.1%, 57th), and it's giving up a similar rate of explosive plays as last year but those plays are going for more yards (109th in IsoPPP).

Here's a good example of how this is all coming together (or not quite coming together) for Nebraska this season. Colorado's first touchdown drive of the second half started from its own 25. Nebraska got a 9-yard sack on the first play, immediately increasing its odds for getting off the field on that drive. The Buffs threw incomplete on second down then hit for 20 yards on third down.

Nebraska won the ensuing first down (a 2-yard run), but then gave up a pass of 19. The Huskers again won the ensuing first down (a 1-yard run), and forced an incompletion on second. After a CU penalty made it third-and-14, the Buffs hit for 37 yards through the air to reach the Huskers' 11.

Nebraska again won on first and second downs (runs of 0 and 3 yards) only to lose on third-and-7 when Colorado threw an 8-yard touchdown. Colorado's success rate on that drive was 36.4 percent, but it still ended up with a touchdown thanks to big plays when it was behind the chains.

And that, in many ways, is Nebraska's season in a nutshell to this point. The Huskers are doing some of the things they need to do to tilt the odds in their favor, then giving those advantages back with key misses.

But if the question this week is "are the Huskers improved?", the answer at the end of the year won't be in the three big gains Colorado had on that drive or the Huskers' inability to get off the field on third-and-long. Those are the easy ones to remember. More important for Nebraska's long-term future, in my opinion, are the seven plays it won on that drive. Keep doing that and the rest should come.

The Huskers have immediately added the sacks and tackles for loss back to the equation under Chinander. The takeaways will be there eventually. Explosive plays? I don't know how low this brand of defense will ever rank in that regard, but that part of it is meant to be neutralized to some degree by a high-scoring offense.

Nebraska doesn't quite have that part yet, either.

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