A large portion of the discussion regarding the current DC search revolves around whether candidates will be able to successfully defend Big 12 Offenses. Chris Ash has been at the center of these discussions, and a fairly common belief is that Ash's success in the Big 10 will not translate well to the Big 12 because he defended worse, more simplistic offenses in the Big 10.
Of course, we're just a bunch of arm chair experts that don't actually know anything, so let's see if the numbers support our distrust of Big 10 DC's in any way.
Quick Note: Stats ahead. I'll be spoilering large portions in order to make this readable. I thought about doing actual statistical testing, but it would have been bad science for several different reasons, so I decided not to. So, there won't be any claims about whether the difference in the performance of Big 12 offenses against Big 12 and Big 10 defenses are statistically significant. I'm guessing that they are not. However, a lack of significance does not mean that the difference does not matter in real life. Football is a game of inches after all.
There were a total of 15 games played between Big 10 and Big 12 teams since the 2015 season. I recorded the points scored, total yards gained, passing yards gained, and rushing yards gained. I also went back and did the math to find each team's average in conference playfor those categories. I've put all of those stats as well as a couple notes in the following spoiler:
So, how did Big 10 defenses hold up when compared to their Big 12 counterparts? Pretty well.
In these 15 games, Big 10 defenses held their Big 12 opponents to 2.9 fewer points and 8.4 fewer yards
If you look at the chart in the next spoiler, you'll see that rush yards + pass yards ≠ total yards but I'm not going back through all this to find like 10 misplaced yards
However, if you remove the Cy-Hawk games from the equation, then there's a slightly different story.
In the 10 games not involving Iowa/ISU, Big 10 defenses allowed their Big 12 opponents 1.8 more points and 25.0 more yards than their in-conference season averages
I wrestled back and forth on whether to include the rivalry games, but ultimately I think it's best to keep them in the analysis. Regardless, there really isn't a major difference. Big 10 DC's have not fared much better or worse against Big 12 offenses than Big 12 DC's have.
I also ran the numbers for Big 10 offenses against Big 12 defenses, and those results are very interesting.
Big 10 offenses scored .5 fewer points than they did in conference play, although they did gain 18 more yards
The math for passing and rushing yards is wonky again here
If you take out the Cy-Hawk games, Big 10 offenses scored 2.2 fewer points than they did in conference play while gaining 3 more yards
Not a huge difference, but that certainly undercuts the "they don't play D in the Big 12" narrative.
Alright, let's talk about what we can take away here.
It's incorrect to definitively say that Big 10 DC's perform worse against Big 12 offenses than Big 12 DC's. There is a lot of context and nuance, but the idea that a Big 10 DC is going to be lost trying to stop a Big 12 offense isn't supported by the last five years of games.
How you choose to incorporate this post in to your opinion of Chris Ash is your own decision. I still don't want to hire the guy for reasons beyond his Big 10 background, but it seems that talking point is a bit overblown.