When college basketball fans think about Notre Dame this season, there are likely a few things that tend to come to mind: the double-double machine Bonzie Colson, the new and improved Matt Farrell, the clutch Steve Vasturia, and the Irish’s impressive free throw, turnover, and three point statistics thus far.

All of these things tend to focus on the Irish’s impressive production on the offensive end of the floor, and this makes sense considering offense is clearly the strength of this team. The Irish rank 9th nationally in offensive efficiency compared to 78th in defensive efficiency (per KenPom).

I wanted to give the defense a bit of attention, however. What do the statistics say? What should we expect moving forward?

The fact that the Irish have an offense ranked as high as 9th and a defense ranked as low as 78th is interesting. I dug through the data over the last five seasons including this one, and two general (and not overly surprising) trends emerged.

There is a moderate-to-strong correlation between how efficient a team is offensively and how strong they are defensively. This correlation seemed to be the strongest among the top teams in the country (the #1 offensive team is more likely to have the #1 defense than the #100 offensive team is to have #100 defense).

The offensive and defensive rankings over the past five seasons indicate that there is a moderate correlation (.49) between a team’s offensive and defensive efficiency. As the graph shows, there is a particularly large “correlation cluster” of dots for the better teams (rank very well in both efficiencies). This representation is more clear for the second graph which just focuses on this season.

The Irish rank #23 overall in the KenPom rankings, and of the top 25 teams, the Irish are one of only three to have a defensive ranking outside the top 50 (UCLA & Creighton).

It’s not surprising that the best teams tend to excel on both ends of the court. Teams with the best coaches and players should perform well both offensively and defensively.

Additionally, a team that scores well will be able to limit the opposition’s transition opportunities and be able to consistently set up their half-court defense, making it easier for the defense to perform well. Also, if a team plays strong defense/creates turnovers, this can make it easier for the offense.

So why hasn’t this correlation between offense and defense been stronger for the Irish so far this season? What do the statistics say?

Before looking too closely at the numbers, my perception of the defense’s problems was that it didn’t do very well protecting the paint and gave up way too many offensive rebounds. This proved somewhat accurate.

To my surprise, the Irish actually rank 37th nationally in defensive 2-point FG% (43.8%). But as I suspected, the Irish rank 226th in preventing offensive rebounds, giving up offensive boards on 30.9% of opponents’ missed shots.

Interestingly, the Irish have the 8th best free throw rate in the country, meaning that only seven teams allow free throws at a lower rate. Along the same lines, the Irish commit a foul on only 21.2% of possessions, fifth lowest in the nation (VJ Beachem commits the 8th fewest number of fouls per 40 minutes of any player).

The adversity to fouling is clearly a major part of Mike Brey’s coaching philosophy. In the 16 seasons from 2002-2017, there have only been three seasons in which the Irish have had a defensive free throw rate outside the top 15 (among 351 teams). In five seasons, the team has been in the top 5.

A glance at the data tells me there isn’t much of a correlation between defensive efficiency and free throw rate (best defenses can have either a high or low rate). But this strategy definitely has some advantages for the Irish: Fouling less prevents the opposition from getting easy points at the line, and prevents teams from getting into the bonus, where they can rack up more free points. Additionally, this approach could encourage players to play fundamentally sound defense, which doesn’t involve reaching in and fouling for example. Also, super aggressive defensive play tends to work best for super athletic teams, something the Irish are not and have not been.

But maybe the biggest reason Brey has implemented this strategy has to do with the way he manages his lineups. In 9 of the last 10 seasons, the Irish have ranked 300th or lower among 351 teams in “bench minutes played,” meaning Brey has consistently played bench players at an extremely low rate relative to other teams. If Brey prefers to rely heavily on his starters, he logically would want to ensure that his starters don’t get into foul trouble. Thus, this is probably a major reason for the “no foul” strategy.

Another statistical finding involves the fact that the Irish are ranked 36th in the nation in steal percentage but only 181st in overall TO%. Irish teams under Brey have historically generated decent steal rates, but have generated a strangely low number of “non-steal turnovers” (TOs due to offensive fouls, travels, passes going out of bounds, stepping out of bounds, dropping passes, offensive three seconds, backcourt violations, etc.)

In five of the past 15 seasons, the Irish have been last or second-to-last in non-steal TOs. It’s difficult to explain how weird this is. Teams have limited control over how many non-steal turnovers they generate, and it’s a metric that tends to be regarded as pretty random. And if the Irish are getting steals, wouldn’t we expect them to force other TOs as well at a decent rate?

Less aggressive defensive teams might be expected to cause less non-steal TO, however, so maybe it at least makes some sense the “no-foul” Irish have consistently ranked so low.

Maybe the craziest statistic I found involves free throw shooting. The Irish offense ranks number one in the country in FT%. As discussed, the Irish don’t foul much, but when they do, their opponents have hit 77.6% of their free throws. This gives the Irish THE WORST defensive free throw percentage of any team in the nation. Irish opponents hit a higher percentage of their free throws than the opponents of any other team in the country. And the Irish make more free throws than any team in the country. This is a ridiculous statistic that really has no explanation. Maybe Irish fans need to do a better job distracting opposing shooters.

So what do we make of Notre Dame’s defense?

I’m not going to try and break down every defender individually, but in general, the team is not made up of outstanding defenders. Therefore, I wouldn’t expect the Irish to defend at an elite level moving forward.

If the Irish offense continues to play well, this should continue to make things easier on the defense. Perhaps the “efficiency correlation” will result in a sort of regression to the mean (Irish defensive efficiency will naturally improve to correlate with the offense). But it is also very possible that Notre Dame’s personnel makes it much better suited for offense than defense, and the disparity in efficiency rankings will continue.

For reasons discussed, the “no-foul” strategy seems to be a good approach for the Irish. When they do foul, opponents’ free throw shooting should regress to the mean as well, something that should help the Irish’s defensive numbers at least a little.

It’s good that the Irish generate steals at a solid rate. Maybe the Irish will be luckier moving forward regarding non-steal turnovers, but it’s possible the past trend will continue.

Regarding the Irish’s 37th ranked defensive 2-point percentage, I’d be very surprised if the Irish still rated this high by season’s end. I think protecting the paint remains very much a significant weakness.

The Irish typically play man-to-man defense, but over the past five games or so, the defense has been going to a 2-3 zone occasionally throughout the game. The zone is typically first unleashed with about 5 minutes remaining in the first half. Then, depending on how the opposition handles it, the Irish will either play zone for an extended period of time or go right back to man-to-man. The Irish have even gone back-and-forth from man to zone multiple times throughout a given game to throw the defense off.

The zone has been fairly effective. At the very least, switching to the zone throws offenses off a bit for the initial possession. The Irish zone isn’t anything too special, but it can have success against average offensive teams that struggle to adjust mid-game. In these situations, the Irish might play a lot of zone. Against, better offensive teams, however, I don’t see the zone holding up for long. But again, it is effective in that it forces the opposition to make some adjustment.

So what should we expect from the defense moving forward? Shockingly, I don’t know. But I do think the strategic aspects of limiting fouls and using the zone occasionally are definitely beneficial. Regarding protecting the paint and limiting offensive boards, more minutes for Martinas Geben/Gleyber Torres could help. But as I’ve discussed in previous posts, these lineups might be worse off offensively. And as I discussed in this post, the offense’s success may play a considerable role in helping the defense.