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Stats O’ War: The five elements of the optimal Big 12 defense

Stats O’ War continues the march to the season, this week discovering what it takes to succeed on the defensive side of the ball previewing the Big 12’s defensive units.

As the college football season approaches, I am analyzing the on-field intricacies of all 10 Big 12 teams to better inform a careful and thorough watching of the upcoming season and to better predict what fans might see in the conference this fall. Last week, I concluded my three part offensive analysis (First Down, Second Down, and Third Down), and now I move to the defensive side of the ball.

The Big 12’s reputation for defense is wanting, in that opposing conferences and fans send up a common refrain; specifically, the Big 12 doesn’t play defense. Careless observers look at blunt and gaudy total statistics and conclude that the conference has no defensive backbone, that the Big 12 plays “football on skates”, and ultimately, that the best teams in the Big 12 have a fatal flaw by design.

I am here today to advocate for the Big 12 as a defensive conference, approaching the matter of optimal defensive philosophy and actual defensive performance on that path.

I’ll begin with some credit where credit is due: reading and research for this article lead me to a 2018 treatise on the five elements of the optimal college football offense by RedmondLonghorn of CFB Data Lab, who can be found on twitter under either of those names. Longhorn’s conception of the optimal offense relies, as often football metrics seem to do, five factors: Quarterback as a run threat, Optionality, Simplicity, Space, and Pace. Together these five create synergies, or what we might call multiplicities, that exponentially increase the quality of an offense. In layman’s terms, any one of these factors increases team quality, but adding additional factors increases beyond the sum of the parts. (In economics speak, we’d call that increasing returns to scale.)

I’ll urge you to go and read the whole post, as it applies to the Big 12 as well as anywhere, and gives the reader a few focal points for watching offenses on the field.

Initially, I planned to use that piece as a guide for this post and for evaluating defenses. As I began preparing data, I thought deeper about the concept, and instead will mimic Longhorn, proposing my own theory of the optimal defense.

Theory of the Optimal (Big 12) College Football Defense

In the spread-heavy confines of the Big 12, a defense must excel in, you guessed it, five factors: Bend-Don’t-Break, Coverage to Check-downs, Run-Stopping, Turnovers, and Eliminate Fatals.

Bend-Don’t-Break: Perhaps the most overused phrase in college football, Bend-Don’t-Break is the key to defensive success in the Big 12. It’s not enough to have an attitude of preventing teams from reaching scoring opportunities; the excellent defense realizes that goal is unfeasible and instead focuses on limiting scoring opportunity conversions.

  • Metrics to look at: conversion and success rate in scoring opportunities, success rate by play number

Coverage to Check-downs: Big 12 teams are going to pass. Big 12 teams are going to spread you out and then try to beat you deep. Many times, the best a secondary can do is force a quarterback from a longer throw into a shorter throw, and many times, that’s a success. Shortening an opponent’s attack through solid coverage distorts their game plan, and a sure secondary can be the foundation of an enhanced pass rush. This corresponds to Longhorn’s ideal of Optionality: pushing teams into second and third offenses can often be a spatial advantage for a defense trying to disrupt a game plan.

  • Metrics to look at: Sack rate, success rate on passing downs, passing success rate, average length of target on completion.

Run-Stopping: The conference reputation for passing does not mean that a successful defense can ignore the run. In fact, a feature of elite teams in the modern Big 12 has been mobile, dual-threat quarterbacks (As former TCU-OC Doug Meachem pointed out on Twitter today: defending “Mahomes, Mayfield, Hill, Boykin, and Murray” is a tall task for any defense, on both passing and running levels). Limiting the rush can curb a dimension of an opponent’s strategy, and limiting the quarterback rush with your front seven frees up your secondary to be more aggressive in coverage. The run stopping feeds the pass stopping in a virtuous cycle.

  • Metrics to look at: QB rush yards again, rushing success rate, success on standard downs, rush percent against.

Turnovers: I cannot say more than has already been said about the prominence of turnovers in the Big 12; in 2018, 23 conference games were decided by one score, and turnovers factored heavily into every game. Aggression in turnovers is a key pillar of a successful Big 12 defense, mostly for the indirect effect of preventing a scoring opportunity for your opponent.

  • Metrics to look at: Fumbles recovered, Interceptions, Interception rate, fumbles above average, interceptions above average, fumbles above expected.

Eliminate fatals: This goes hand in hand with the above bend-don’t-break philosophy. Big plays are a fact of life in the conference, and with the pace of play, quite a good number of big plays can be expected every game. A successful defense will need to effectively limit the damage of a big play and recover when they do give up a big play.

  • Metrics to look at: Big play rate, average length of big plays, success rate after big plays, percentage of scoring drives with big plays.

Big 12 Defenses

So, of course, to characterize each Big 12 team by each of the metrics above in a comprehensive manner would require some undue (and perhaps excessive) effort and real estate. What I propose instead is to select what I consider the two most important metrics from each category and add some commentary along the way. With no further ado:

  1. Bend-Don’t-Break

Success By Play Number:

85% of drives in non-garbage time in 2018 in the Big 12 (lots of qualifiers, I know) were resolved in 8 or fewer plays. I use that as my threshold for bend-don’t-break, and I get the following two lists.

Top 5 Bend-Don’t-Break Defenses (Success Rate after 8 Plays)

Texas (44%)
Kansas (46%)
Texas Tech (46.2%)
TCU (46.9%)
Oklahoma State (48.9%)

Top 5 Bend-Don’t-Break Defenses (Scoring Opp Conversion Rate):

Iowa State (6.5%)
TCU (8.4%)
Kansas State (9%)
Kansas (9.3%)
Oklahoma (9.4%)

2. Coverage to checkdowns

Top 5 teams in sack rate:

TCU (8% of pass attempts)
WVU (6.8%)
Iowa State (6.7%)
Texas Tech (5.8%)
Baylor (5.77%)

Top 5 teams in average distance of completion:

Iowa State (8.206 yards)
TCU (8.745)
Kansas State (9.957)
West Virginia (10.07)
Texas (10.144)

3. Stopping the Run

Top 5 teams in Rushing Success Rate:

TCU (44.3%)
Iowa State (46.17%)
West Virginia (48.2%)
Baylor (48.6%)
Oklahoma State/Texas (tie) (49%)

4. Turnovers

Top 5 teams in interception rate:
Kansas 4.86%
WVU 3.76%
TCU 3.26%
Kansas State 2.85%
Texas Tech 2.1%

Top 5 teams in Expected - Actual Fumbles:

Kansas (+2)
TCU/Iowa State (tie) (+.5)
Oklahoma State/Oklahoma (tie) (+0)

5. Eliminate Fatals

Top 5 teams in Big Play Rate:

TCU (10.9%)
Iowa State (11.68%)
Oklahoma (11.89%)
Kansas State (12.48%)
Texas (12.52%)

Conclusion

What have we learned? The first observation an astute reader will make is that one team found itself in the top five in all lists presented above: that’s right, anyway you statistically slice the Big 12 defensive landscape, TCU is at the top. Many teams have their unique strengths - Texas Tech in interception rate, West Virginia in average distance of completion, or Baylor in sack rate - but on the whole, two defenses stand above the rest: TCU and Iowa State. (Kansas State finds itself in a lot of these lists, and they had a sneakily-decent top 60 defense.)

Additionally, what I’ve provided above is a framework for watching a game. Defenses in the Big 12 can be perplexing, and concepts like total defense and pace-adjustments are misapplied and misread left and right (hello summer of 2017 Lincoln Riley). Looking through this lens, we can direct our attention to some specific box score items to help us truly understand which defenses held up against the Big 12 offensive onslaught. In fact, if you look long enough, and squint your eyes just right, you might even see that the Big 12 in fact does play some pretty competent defense.