Can a coach do anything about the 3pt shooting % of his opponents? Is that solely based on luck?

This has been one of the hotly contested topics around the NBA for several seasons, including with the Bucks this season. I don't claim to have the answer, but I do have some data that could lead to some interesting analysis, which I think is worth your time to read over.

I analyzed the season-long opponent 3pt% for every coach for the last 3 seasons. Then I put that in a table. So, this is sorted by coach more than by team (though not many coaches were the head coach for multiple teams in the last 3 years). You might point out that this is influenced by roster and potentially assistant coaches, not just who the head coach is, and you're absolutely right. However, I still think this is worth looking at and reflecting on.

I also added the playoff results from the last two playoffs (since we don't have the 2021 playoffs yet and 2018 would've been a different roster and coaches than the regular season data I'm looking at. In this table, I just lumped all playoffs from those two years together, since the playoffs are such a small sample size. This might sound hugely problematic, but I think the results are fascinating, as they track with the regular season results very closely.

Finally I averaged each regular season and the total playoffs into one figure (so an average of 4 data points...3 regular seasons and 1 averaged playoff number). I then color coded the chart, because that's fun and easier to read, and sorted it by that "total average." Remember that this is opponent 3pt%, not the 3pt% that this coach's team shoots. Also keep in mind that this data was from mid-February, and things can change rapidly in the NBA. I'll try to do it again at the end of the year. With that said... Enjoy!

So, what jumps out?

It is hard to make any definitive statements of course. However, this is a large set of data, so I think we can at least conclude that there seems to be an indication that some coaches seem to be doing a better job controlling opponent 3pt% than others.

With this being a very large sample size, I would not expect luck to be much of a factor at this point, even though it might be for a single regular season or playoff.

Additionally, it is often stated anecdotally that Brad Stevens seems to get the Celtics to defend the 3 very well, and the data bears that out. When the data supports assumptions, that is always worth considering in my opinion.

Which coaches are best at limiting opponent 3pt%? What is fascinating to me is that in spite of that stat's seeming-importance, there is little correlation between limiting opponent 3pt% and not being fired. In fact, only 1/4 of the top four coaches are currently employed by their team.

Kerr and Popovich, two titans of coaching, do not grade out favorably in this analysis. On the other hand, Stevens and Nurse do look fantastic. Before the Raptors slump this season, both were in the blue every year.

D'Antoni was famous for his switching defense in Houston, which appeared to be successful both in the regular season and playoffs at limiting opponent 3pt%. You might think of small ball with PJ Tucker at center, but he started Clint Capela for 1.5 seasons of his 2 regular seasons worth of data, including the stronger season.

Brett Brown did not play small ball at all, and instead did the opposite. He did have a very strong defensive team, with Embiid as an amazing anchor and Simmons providing a lot of length on the perimeter, so perhaps that plays a role?

Stevens has used a lot of more mobile center minutes these seasons, with Horford and Theis, though Baynes was frequently the starting center with Horford at PF. The Celtics also had big wings.

Nurse started several different guys, including Valanciunas, Ibaka, Gasol, and now Baynes in the down year. Gasol had the largest sample size as the starter, and is not particularly mobile/quick. The Raptors start two short, but strong, guards, but started Danny Green, a longer guard, along with Kawhi two seasons ago.

Bud, predictably, isn't elite on this list. He's around the middle of the pack, though pretty good last season. He's sandwiched between Clifford and Casey, who are both respected coaches, though not exactly brilliant.

Quin Snyder, who is generally revered as a brilliant strategic coach. Snyder has one of the oddest data sets on the list, as his regular seasons are all strong, but playoffs are terrible. Nate McMillen has very similar numbers; those two coaches are not generally thought of the same way.

Does this data actually lead to any conclusions?

Yes, I think it does.

• Opponent 3pt% is not completely random; some coaches have consistently good results against 3's, and I do not believe that to be luck. The same few coaches are elite year after year, while the worst coaches are predictably awful against 3's.
• Therefore, it should be possible to construct a defensive scheme that gets better results against 3's than what the Bucks currently have. Perhaps the Bucks are already heading this way; their opponent 3pt% has dropped from 38.3% when I got this data to 38% when I am writing this fanpost, though that isn't exactly a groundbreaking drop.
• Is luck involved? I think luck could absolutely be involved in a single game shooting. But over the course of an entire season, and certainly multiple seasons, I think this data clearly shows that luck is ironed out and some coaches (Stevens at the forefront as a 3 year example) know how to prevent a high opponent 3p%.
• I don't think a particular type of defense has to be played to get good results; however, I'm not a scheme expert and don't know what all these elite teams do on defense. If someone is, I'd love to hear more. What I would imagine though, is that the answer is more simple than a grand scheme; it is perhaps merely about where the primary defensive emphasis is placed.
• The coaches who got fired didn't win enough games; perhaps focusing primarily on opponent 3pt% is misplaced, when it comes to winning games? That is a different topic, but worth considering too...