UNC’s below-average 3-point percentage defense might not tell whole story

On paper, at least, it looks like a clear mismatch, perhaps the one of greatest concern for North Carolina entering its game against Indiana on Friday in an NCAA tournament East Region semifinal.

The Hoosiers are one of the best 3-point shooting teams in the country, and they make 41.6 percent of their attempts. The Tar Heels, meanwhile, rank in the 200s nationally in 3-point field-goal percentage defense, and opponents have made more than 35 percent of their attempts from beyond the arc against UNC.

So, advantage Indiana, right? Maybe not.

Marcus Paige, a Tar Heels senior guard, found himself curious about the question Tuesday. A student of advanced statistical analysis in college basketball, Paige began searching on Google for information about 3-point field-goal percentage defense, and whether it’s a viable metric.

He came across an article Ken Pomeroy, a popular college basketball statistician, published in 2012 on kenpom.com. Pomeroy’s article, aptly headlined “ ‘3-point defense’ should not be defined by opponents’ 3P%,” challenged the notion of 3-point field-goal percentage defense.

To be more precise, the article disputed the metric.

“(Three)-point defense or 3-point field-goal defense is not something that’s always in control of the defense,” Paige said. “I don’t know if you guys are into statistics and stuff like that. It’s definitely a concern of ours, and the only way to really impact that is to limit the number of attempts they get.”

That was the premise of Pomeroy’s article: that a team’s ability to defend 3-pointers is more accurately reflected not by the percentage of attempts the opposition makes but by how many 3s opposing teams attempt.

Indiana has excelled at making 3s this season. And about 40 percent of all of its attempts from the field, according to kenpom.com, come from behind the 3-point line. Among the 16 teams remaining in the NCAA tournament, Indiana attempts 3-pointers at the fourth-highest rate, according to kenpom.com.

One of UNC’s defensive priorities Friday, then, will be to limit Indiana’s 3-point attempts.

“That’s what they want to do,” sophomore forward Justin Jackson said Tuesday of Indiana’s desire to shoot a high amount of 3s. “So we’ve got to make everything as hard as possible against them.

“But as far as the stat – I don’t really know much about that.”

He was talking about 3-point field-goal percentage defense, which Pomeroy concluded to be as useless as free-throw percentage defense. And yet while teams aren’t held accountable for the percentage of free throws another team makes, 3-point percentage defense is held to a different standard.

Jackson called it a “weird stat” – that UNC ranks 223rd nationally in 3-point defense. Last season, UNC’s opponents made 30 percent of their attempted 3s, and the Tar Heels ranked 14th nationally in 3-point field-goal percentage defense. Jackson used that word again: “weird.”

“That’s weird because our defense is better this year than it was last year,” he said.

By all other measures, UNC’s defense has improved significantly from a season ago. The Tar Heels ranked 51st nationally in adjusted defensive efficiency last season, according to kenpom.com, and they’re 10th entering their game Friday. For 27 consecutive games, not one of the Tar Heels’ opponents have made more than 45 percent of their attempts from the field.

And yet UNC’s opponents have made enough of their 3-point attempts to suggest the Tar Heels have difficulty defending the perimeter. But do they, really? And, if so, what’s different about UNC’s perimeter defense this season compared with last?

“I think we had personnel – J.P. (Tokoto) was great last year, our perimeter defense was really good last year,” Paige said. “But this year our entire defense is overall better. And I think – I don’t know – it’s hard to explain why our 3-point defense can be 200 spots different from one year to another.”

That opponents are making a higher percentage of 3 attempts against UNC hasn’t especially hurt the Tar Heels. They’ve won eight of the 10 games in which opposing teams have made the highest percentage of their 3-point attempts.

The best way to explain opponents’ 3-point success against UNC might be luck. Pomeroy concluded that while defenses possess some control over how many 3-pointers an opposing team attempts, they have little control over the percentage of 3s an opposing team makes.

After reading Pomeroy’s article, Paige began a conversation with Jackson about 3-point defense.

“I don’t know why,” Jackson said with a smile.

The topic was on Paige’s mind. He said he was in the Student Union at UNC when his Googling led him to Pomeroy’s article. Paige was searching for insight into a question that’s of concern for the Tar Heels, especially this week: Is their 3-point defense really as much of a liability as the numbers suggest?

Perhaps not. Against Indiana, after all, the effectiveness of UNC’s perimeter defense might not be measured in the percentage of shots the Hoosiers make. It’s more likely to be quantified by the 3-point opportunities UNC eliminates before Indiana has a chance to attempt the shot.

This story was originally published March 22, 2016 at 7:07 PM with the headline "UNC’s below-average 3-point percentage defense might not tell whole story."