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Peering through the glass: Examining Northwestern’s rebounding issues and its unique statistical profile

Northwestern’s struggles down low contribute to an identity that’s... weird. What does it mean?

NCAA Basketball: Chicago State at Northwestern David Banks-USA TODAY Sports

Over the past week, Northwestern men’s basketball’s Christmas list of concerns got much longer. Consequently, an item that’s been near the top of that list since early November — rebounding — has gotten a little blurry.

Whether it got obscured from the larger-scale panic arising from an inexplicable loss, Northwestern’s rebounding problem got clearer in its past two games. Against Chicago State and DePaul, two teams that were getting outrebounded by over five boards per game prior to their tilts with NU, the Wildcats lost the combined rebounding battle. With the heart of the Big Ten schedule looming, it’s worth diving into those issues, and how they’ve contributed to what is looking like an eerily unique identity for Northwestern.

First off, how bad are these struggles, really?

The answer: it’s not great, but it could be worse. When it comes to offensive rebounding percentage and allowed offensive rebounding percentage — which are better metrics than raw rebounding totals to evaluate slow-pace teams that tend to generate fewer possessions like Northwestern (more on that later) — the Wildcats rank outside of the nation’s top 220 teams. They’ve allowed opposing offenses to secure 31.2% of potential defensive rebounds. There happen to be 15 Power Six teams with a worse defensive rebounding percentage, including three Big Ten teams (Penn State, Rutgers and Maryland). That’s not horrible.

However, none of those teams have played an easier slate of games than Northwestern, which has KenPom’s 284th-highest strength of schedule rating through Dec. 18. Of course, even that mark is buoyed by NU’s lone conference game against No. 1 Purdue. Even worse, nine of Northwestern’s 12 opponents on the docket before the new year (including Dayton and Arizona State) have defensive rebounding rates that fall outside of Division I’s top 220.

Comparing this to Northwestern’s recent program history, this is a little concerning. As stated above, the Wildcats’ opposing offensive rebounding percentage in 2023-24 stands at 31.2% thus far (not shown here):

Data and graph courtesy of Bart Torvik (barttorvik.com)

Northwestern has already played six of the seven (currently) Quad 4 games on its schedule, has 19 Big Ten games left and is already on pace for its worst defensive rebounding percentage since Bill Carmody roamed the sidelines. Not good!

It’s easy to attribute these struggles to Northwestern’s lack of a traditional power forward. After all, you can see NU’s defensive rebounding success climb in seasons where Chris Collins deployed two-big lineups (Robbie Beran-Matt Nicholson, Beran-Pete Nance). Yet, although size is important, it hasn’t proven to be the be-all and end-all for the ‘Cats.

This is far from the first season where Collins has gone small. In fact, Northwestern has gone multi-year stretches playing even smaller. Bart Torvik has a metric called effective height, which weights the minute totals of a team’s frontcourt (effectively, the average of the “tallest 40%” of its minutes). This season, NU’s effective height sits at 6-foot-8 12 (not shown). It’s small, but it doesn’t beat the Dererk Pardon era. The gray dots represent the Big Ten average, which is currently at 81.1 inches this year:

Bart Torvik

Even if you’re of the mindset that this metric doesn’t take the 2023-24 Wildcats’ lack of two-big lineups into enough account — which is totally fair — Northwestern’s average height weighted by total minutes (77.3 inches) is comparable to a season like 2021-22, when it rebounded well:

Bart Torvik

While it’s true that Northwestern has tended to rebound better when it grew, there’s seasons like 2019-20, when the Wildcats didn’t clean the glass at a great rate despite possessing significant size advantages across the board. Additionally, Collins and Co. maintained respectable rebounding marks when they rolled with the 6-foot-8 Pardon — a terrific rebounder — at center for three straight seasons. On the 2016-17 squad, not a single player that earned more than 10 minutes a game was taller than 6-foot-8.

Thus, not having a true four makes a difference, but as Collins has noted when he’s been asked about Northwestern’s struggles on the glass, it’s not the primary root of the problem. The ‘Cats have won before with these issues, and they did in 2016-17.

What’s unique about the rebounding struggles this season — and maybe worrisome — is that Northwestern is doing this at a pace that’s super slow, even by its own standards.

By nature, a shorter, perimeter-centric team tends to play at a faster pace. More possessions equals more shots, which creates more opportunities to excel for a team that believes it can outshoot its opponents. Although small rebounding issues might hurt, they won’t be fatal for a team if it can defend well and score at a significantly higher clip with lots of chances to prove itself.

An individual defensive rebounding opportunity means slightly less for a fast-paced team than it does for a slow-paced one like NU, which seeks to limit the number of possessions in a game and has fewer chances to score. The fewer possessions in a game there are, the more valuable each one becomes. It also makes preventing extra ones all the more important, which is why Northwestern places such an onus on avoiding turnovers. As a result, the Wildcats’ lapses down low are especially significant.

As a team with four perimeter players standing 6-foot-6 or smaller in its starting five and the second-slowest adjusted tempo in the Power Six, Northwestern is already weird. This is a little weirder:

(A UVA-Northwestern noncon game absolutely NEEDS to happen)
Bart Torvik

Northwestern hasn’t just struggled to grab defensive rebounds in pre-Big Ten play. It’s also done that while playing some of its slowest basketball in nearly a decade. And, if the past few years mean anything, its pace could slow even more come January. The Wildcats have surrendered 31.2% of their potential defensive rebounds while playing at an adjusted pace of 64.5 possessions per game through Dec. 18.

This is incredibly unique. A grand total of one Power Six team since 2015-16 — 2023-24 Virginia — has had both a lower adjusted tempo and a higher opposing offensive rebounding percentage through that date. The rigors of conference play brought only four other teams past both of Northwestern’s marks over a full season since 2015-16.

Here’s a quick look at those teams:

  • 2023-24 UVA (9-1, 32.6 OOREB%, 61.6 AdjT as of Dec. 18) — Tony Bennett’s gift. No starter taller than 6-foot-8. One rotational player bigger than that. No. 2 in KenPom’s adjusted defensive efficiency. Almost lost to Northeastern.
  • 2022-23 South Carolina (11-21, 32.5% OOREB%, 64.2 AdjT) — Went 4-14 in the SEC.
  • 2019-20 Texas A&M (16-14, 31.8% OOREB%, 64.4 AdjT) — KenPom’s 77th-best defense. It also had the 10th-highest luck rating in Division I.
  • 2018-19 Florida (20-16, Round of 32, 32.2% OOREB%, 61.8 AdjT) — KenPom’s No. 16 defense. No player on the entire roster taller than 6-foot-9. Four of five starters stood at 6-foot-6 or smaller.
  • 2015-16 Oklahoma State (12-20, 32.3% OOREB%, 64.2 AdjT) — Went 3-15 in the Big 12. No player on the entire roster taller than 6-foot-9. Its luck rating was Division I’s seventh-worst.

That’s not exactly a recipe for success. It makes sense: a slower tempo without a dominant big makes it harder to generate efficient offense, which makes it even tougher to defeat good teams that can break down almost any defense. The two NCAA Tournament-bound teams in that group have elite, quick and versatile defenses, while Northwestern’s has not looked the part without Chase Audige. For the ‘Cats to survive in Big Ten play, let alone get to March Madness, their rebounding and/or perimeter defense will almost certainly need to improve as it works against the grain. That’s immensely difficult.

Okay, that’s a lot of negatives. Here’s some optimism: Arizona State presents another get-right opportunity on the glass for the ‘Cats. The Sun Devils have failed to secure over 32% of their potential defensive rebounds. While their starting lineup is smaller than Northwestern’s, ASU’s 30% three-point clip indicates it may not be able to stretch the floor enough to force Nicholson out of the game.

Plus, Northwestern is slowly trending upward in the rebounding department. After only securing 69.2% of its defensive boards against Chicago State, the ‘Cats snagged 75.8% of DePaul’s missed attempts. With the exception of the Purdue rebounding battle (which, to NU’s credit, was pretty much impossible to keep close), Northwestern has played up to its competition on the glass.

In order to ensure their perimeter stars get enough possessions to bring home victories, the Wildcats will need to set a solid foundation for their team rebounding in their final two nonconference clashes.