Chad Holderfield doesn’t know who I am, and we will probably never meet, but his tweet was the influence for this blog post. Well, Jordan Sperber deserves some credit too. Chad’s tweet was in response to Sperber, who, by the way, is a fantastic follow for any basketball fan.
Sometimes the best ideas come organically while scrolling through social media. Thanks, Jordan and Chad!
Sperber’s original post was about teams that basically disregard the three-point line on defense but are still able to prevent their opponent from scoring. In other words, lockdown defenses that don’t really guard the arc. You can (and should) read the whole piece here. The 18-19 Virginia Tech team was an extreme case of this, and was the focus of his post.
Chad then wondered if these teams are better at defensive rebounding. Presumably these are teams that pack it in and protect the paint, so that would make intuitive sense. Packing it in means staying between your man and the hoop, which should leave you in good rebounding position. Of course, as Sperber pointed out in our thread, zone-exclusive teams like Syracuse are also likely to fit the mold, and the Orange certainly have trouble boxing out.
That being said, man defense is much more common than zone defense, so I still expect teams that give up threes to rebound better on the whole. That probably means we’re heading towards one of those blog posts where I pretty much find out exactly what we thought was true is, in fact, true, and no one learns anything new. (I must’ve been sick the day we learned about hooking the reader in Englsh class.) Nonetheless, curiosity prevails, and besides, I can’t let Chad down!
For starters, let’s define which specific teams we’re talking about here. I let Chad pick the arbitrary cutoffs, so if you don’t like them you can direct all hate mail his way.
We are going to define the lockdown defenses as those that ranked in the top 25 in KenPom’s adjusted defensive efficiency for that season, and teams that don’t guard the arc as teams in the top 150 in highest opponent three-point rate. There have been somewhere between 7 and 12 of those teams every year in KenPom’s database (2002-19) for a total of 160.
Of course, top-25 defenses are going to be better at defensive rebounding than average teams whether they prevent threes or not, so let’s start by comparing the elite defenses that guarded the arc to the elite defenses that didn’t. Because I hate long and awkward-sounding names and I’m too lazy to come up with a better solution than made-up acronyms, I’ll call the arc-guarders AGs and the non-arc-guarders NAGs. Here are the results:
The NAGs did rebound better than the AGs, but the gap wasn’t quite as big as I thought it would be. In fact, in 7 of the 18 seasons the AGs actually rebounded better. Over half of the Syracuse teams in this timeframe are included, but that still only accounts for 10 of the 160 NAGs. The overall average for NAGs was 69.95%, and for AGs it was 69.42%. That is close enough that it’s time for some good ol’ significance testing. A two-sample t-test gives us a p-value of .00007, so the difference is real. If you are new to this blog or to statistics, that means that our sample is big enough that the small difference in rebounding percentages matters quite a bit.
Now that we’ve confirmed that elite defenses that still give up threes really do gain a rebounding edge, let’s forget the arbitrary groupings and look at this relationship among all defenses. The r² value for the correlation between opponent three-point rate and defensive rebounding percentage is just over 0.25, which means over a quarter of a team’s defensive rebounding percentage can be explained by how often it gives up three-point looks. With 6,157 team-seasons in the KenPom database, 0.25 is extremely meaningful. Here is a plot of all 6,157 teams.
The blue line is the trendline, showing the increase in defensive rebounding percentage as teams allow more threes. Those logos are just for kicks and giggles–all 18 of Jim Boeheim’s Syracuse teams are below the trendline, and all of Tony Bennett’s teams are above it. Boeheim and Bennett are probably the most well-known zone and packline coaches, respectively. If I had either a Sperberesque attention to detail or a bunch of interns to do my bidding, I’d go through all of these teams and separate them into bins based on defensive scheme–the zones, the packlines, the denials, etc. Instead I’ll just leave that idea dangling to keep you up at night.
There’s another Bennett I want to spotlight before I wrap up. Randy Bennett of Saint Mary’s stands out as a coach who doesn’t like to choose. He was probably that kid who took one of every color sucker at the bank, because he couldn’t choose just one. While his colleagues are choosing whether to give their opponents open looks from deep or second-chance opportunities, he is taking away both. Here’s the chart with Randy Bennett’s data points on it:
There you have it. Taking away threes does seem to come at a rebounding cost, although it’s certainly possible to be good at both. That tends to be the beauty of basketball. There are endless different styles of play, and they all involve giving up something to improve something else, but it’s always possible to be good at both with the right combination of skill, effort and coaching. While most teams that run their opponents off the three-point line will have to live with the offensive rebounds, there will always be Randy Bennetts that find ways to get the best of both worlds.
Follow me on Twitter at @cwetzel31 for more hoops content.