The most important question surrounding North Carolina at the start of last season was this: How much could the Tar Heels’ defense, so miserable in 2014, improve in its first year under defensive coordinator Gene Chizik?
The answer turned out to be “significantly.” The Tar Heels went from 117th nationally in yards per play (6.53) in 2014 to 56th (5.50) a season ago. The defensive turnaround, particularly when it came to reducing the number of blown coverages against the pass, was a key factor in UNC’s 11-win season.
The turnaround, though, was one-sided and limited, essentially, to pass defense. The Tar Heels gave up 8.5 yards per pass attempt in 2014, a staggering number that was the worst among Power 5 conference teams. Overall, UNC’s pass defense ranked 121st nationally in yards per pass attempt.
Last season, in its first under Chizik, UNC allowed 6.1 yards per pass attempt, which ranked tied for 15th nationally. In the ACC, only Florida State, which allowed 5.6 yards per pass attempt, had a stingier passing defense on a per-pass basis.
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The Tar Heels’ run defense, meanwhile, did not see significant improvement. It allowed 5.22 yards per carry in 2014 and ranked 108th nationally there. Last year it improved slightly (5.13 yards per rush) and ranked 109th nationally in yards per carry.
And so the main question facing UNC this year is a variant of the one from last year. Last season, it was how much the entire defense could improve. This year, it’s how much can the run defense improve in Chizik’s second season? That was the focus of a story I wrote here.
As I wrote in that story, there’s a precedent for significantly improved run defenses in Chizik’s second season as a coordinator. That’s what happened at Auburn in 2003, in Chizik’s second season there. And that’s what happened at Texas in 2006, in Chizik’s second and final season there.
Let’s take a closer look at the past so it might provide some insight about the future – and, in particular, UNC’s future this season defending the run. First up, Auburn’s run defense between 2001 and 2003 (explanation about numbers coming):
▪ 2001: 3.90 ypa; -0.90 dypa
▪ 2002: 3.97 ypa; -0.27 dypa
▪ 2003: 2.81 ypa; -1.27 dypa
First, all of these numbers include games against FBS – formerly Division 1-A – opponents only. The 2001 season was the season before Chizik arrived. The 2002 season was Chizik’s first as defensive coordinator, and the 2003 season his second.
The first set of numbers (ypa) is yards per attempt – the average yards those defenses allowed per rushing attempt. The next set of numbers (dypa) is the difference between what Auburn allowed per attempt and what its opponents averaged per attempt throughout the entire season. The lower that number – the further into the negatives it goes – the better.
For example, let’s say Auburn held its opponents to 3 yards per carry but that, overall, its opponents averaged 5 yards per carry throughout the season. The difference in yards per attempt (dypa) would be -2.0.
As the numbers show, Auburn’s run defense improved significantly in its second season under Chizik. The Tigers allowed a full yard per attempt fewer. The difference between what Auburn allowed per carry and what its opponents averaged during the season also grew, from -0.27 to -1.27.
Now, Texas. Chizik became its co-defensive coordinator in 2005 and stayed for two seasons:
▪ 2004: 3.18 ypa; -1.53 dypa
▪ 2005: 3.69 ypa; -0.78 dypa
▪ 2006: 2.21 ypa; -2.23 dypa
At Texas, like at Auburn, Chizik inherited a defense that was already good against the run. In time, he helped make it better. The Longhorns regressed against the run – but were still very good – in Chizik’s first season but then completely dominated opposing rushing offenses in 2006.
Let’s do the same thing for UNC, looking at the season before Chizik arrived and last season:
▪ 2014: 5.32 ypa; 0.55 dypa
▪ 2015: 5.18 ypa; 0.48 dypa
Again, these numbers only reflect games against FBS opponents. At UNC, they show how dire of a situation Chizik inherited. The rushing offenses that UNC faced in 2014 were, on average, about a half-yard per carry more productive against UNC than they were throughout the season.
That’s not good. That improved slightly last year, in Chizik’s first season, but not all that much. The numbers also provide greater clarity about what was already known: That for Chizik, arriving at UNC was nothing like what he entered at Auburn and Texas.
At both of those places, a good defense – or even a great defense – was already in place. It was the opposite at UNC, where Chizik has had to rebuild. So, what now? How much can UNC’s run defense improve in Chizik’s second season?
At both Auburn and Texas, the run defense took large leaps in Chizik’s second season. Both times, Chizik’s run defenses allowed at least a full yard fewer per carry in his second season than it did in his first.
If the same trend continues at UNC, the Tar Heels this season would allow, at most, about 4.15 yards per rushing attempt. That would place them in the 50s nationally, and would represent a significant improvement – the kind that Chizik has engineered before.