By the numbers: Penalty problems?

Over on his Insider blog, our pal Travis Haney found some concernsInsider with a few of ESPN's preseason Top 25 teams, including one contender from the ACC. Haney isn't convinced North Carolina is ready to turn the corner, and while there are plenty of reasons for concern — the O line, the D line, the youth — he's got a different bone to pick with the Tar Heels.

From Haney:

But the main reason to doubt the Tar Heels being a top-25 team?

"One word: discipline," a coach in the league told me this week. "Too many personal fouls and unsportsmanlike calls."

UNC was 112th in the FBS in penalties per game (7.4) a year ago. That sounds like a product of what coach Larry Fedora calls a "young" team. And it explains why I like Duke more as a top-25 choice, even if the talent balance tips in UNC's favor.

Penalties are a particular annoyance for coaches, and that's often because they view flags and discipline as mutually exclusive — just as this ACC coach did with Haney.

But, of course, there's nuance that comes with penalties, and racking up a bunch of flags over the course of a season doesn't necessarily mean a team lacks discipline.

First off, let's examine the basic stat: Penalties per game. Add up the flags, divide them by games, voila. The problem, however, is that "a game" is not necessarily an equivalent measure among teams. Texas Tech played 13 games and ran 1,135 plays last year. Miami played 13 games and ran 315 fewer plays.

Those same differences can occur on defense, too. Missouri faced 350 more snaps on defense last yfear than its SEC counterpart, Florida.

So let's get a better idea of just how likely a team is to be flagged on a play by adding up all the snaps that occur during the course of a season (offense, defense and special teams) and divide that by its total flags.

What we find is that even for the "least disciplined" teams, flags occur only about 5 percent of the time — or one out of every 20 snaps. That's really not much, which should be our first sign that perhaps the impact of flags is a bit overrated.

But let's stick with the theory a bit longer. Turns out, even if we view penalties as a percentage of total snaps, the Tar Heels don't look too hot. They're ranked 109th out of 125 teams.

Before we bury the Heels' though, let's look at which teams finished with a higher rate of flags. There were some bad ones (USF, Florida, Memphis, Kansas) and there were some good ones (Louisville, UCLA, LSU). In other words, there's not a ton of commonality except, perhaps, this: A lot of those up-tempo offensive teams also had a particularly high rate of penalties. Baylor (123rd), UCLA (120th), Syracuse (119th), Oregon (118th), Washington (115th), Texas Tech (104th) and BYU (102nd) are all tempo offenses and all had a high percentage of flags.

And that makes some sense. When you move fast, you're apt to make mistakes. Obviously most of those coaches are more than happy to make that trade-off, however, even if they'll still moan and gripe about discipline.

The reason they'll make that trade-off is because the tempo helps the offense, and if the offense is going good, the penalties really don't matter. In fact, here's how much they don't matter in terms of comparisons of the 10 most penalized (by percentage of total plays) Power Five conference teams last year and the 10 least penalized.

The yards-per-play stat is perhaps a bit misleading since that's strictly looking at offense, and flags can occur on D or special teams, too. But think of it this way: If you get a flag at any point, that costs yards. So to offset flags, you need to gain yards. And if we even account for lost penalty yardage, the most-flagged group still averages 5.20 yards per play, while the least-flagged group averaged 5.13.

(Though, it's worth noting regarding Haney's direct comparison of Duke and UNC -- the Heels had the 10th highest rate of flags among Power Five teams and averaged 4.99 yards per play after subtracting lost penalty yards, while Duke had the 11th lowest rate and averaged 5.31 yards per play, less penalty yardage.)

Now, we're not the first folks to do this exercise, certainly. And even most coaches know a certain number of penalties come with the territory when your team is playing fast and tough. It's what good teams do.

It's just that they're still apt to complain about the flags because that's what coaches do, too.

"As a team, we will do much better this year," Larry Fedora said. "That is a major point of emphasis for our football team. We're going to play smart. We say smart, fast and physical, but the smart part comes first."