The Muses’ Notebook (Sep. 24)

by Baltej Parmar

For this series, I will be posting research that I’ve looked into and posted on my Twitter but wanted to expand and add some more thoughts about the data. Recently I looked into shot selection for all teams based on league average shooting talent. In other words, how good would each team’s offense be if they made a league average percentage of the shots they took, given the type of shots they took? I created two tables which you can see below. The first table accounts for whether or not three-point attempts were contested by the defense, as well as the location of the shot. Doing should tell us both how “good” or “bad” a shot is in terms of location as well as openness.

Editor’s notes: Is there a major difference between the effect of defensive pressure on two-point shots and the effect of defensive pressure on three-point shots? Since the current table only inspects whether or not three-pointers were contested, the model may neglect relevant data. That said, it is crucial to consider other factors besides location when we evaluate how good or bad a shot is. As much as the analytics community likes to emphasize high-value shots, NBA defenses are geared to prevent those shots. Responsible analysis has to find some way to come to grips with this.

The second table only considers location. In this case, we are not concerned with whether or not the defense contested the shot; we only want to know about where on the floor the shot came from.

Some things I noticed:

  • For all the talk of the Spurs relying on ball movement and only taking the open shot, their expected Offensive Rating actually drops once you factor in how contested their threes were (from 99.05 to 98.75). This suggests that it wasn’t necessarily the system or ball movement that was the reason they were knocking down shots at such an elite rate; their success had more to do with the fact that they had elite shooters all around. Their Offensive Rating was 8.12 points better than expected based on their shot quality, which was the 2nd-best differential in the league. The Spurs trailed only the Golden State Warriors, who had a whopping 10.3 point differential.
  • Boston ranking 25th might be indicative of the team’s willingness to buy into Brad Stevens this past year.
  • Orlando desperately needs more playmaking. Hopefully Markelle Fultz can provide them a legitimate offense creator this year.
  • Utah ranked 15th in the difference between actual versus expected. Now that they have subbed out Rubio and Crowder (two of the Jazz’s worst shooters based on the shots they get) for Conley and Bojan Bogdanovic (elite open shooters) a big leap should be coming.

Editor’s notes: The shot-making talent on Boston’s roster last year was outstanding, but the quality of their offense was a well-documented sore spot. Their failure to get to the free throw line (not considered here) was a major impediment. Baltej’s analysis paints a more positive picture for Celtics fans heading into next season. Kemba Walker subsisted on a shot diet fairly similar to Kyrie Irving’s last year, and Boston has three proven shooters who will play big minutes around him.

Utah is a good test case for the marginal value of offense versus defense. Bogdanovic is probably the best jump shooter on the Jazz roster now, but he will be taking minutes that were allocated to Jae Crowder and Royce O’Neale in the past. Can Utah maintain there high defensive standards with Bogdanovic usurping those minutes? If not, will the tradeoff in expected Offensive Rating be enough to offset the decline in Defensive Rating?

Below is a chart that displays how much better or worse the teams expected Offensive Rating is when factoring in contested shots, compared with the same calculation looking only at shot location. In simple terms, this table is providing us with the differential between the first and second tables above.

Some things to note:

  • Houston’s expected rating has the biggest drop, which makes sense considering the number of step-back three-pointers James Harden attempts (6.92/game). Even after taking this into account, Houston still ranks 5th in the league due to the amount of open shots he can create for his teammates.
  • The top three jumps in overperforming expected rating once we factor in how tightly the shots were contested are Atlanta, Milwaukee, and Denver. Trae Young and Nikola Jokic are masters at finding wide open shooters outside the three-point line, which may go a long way toward explaining their teams’ performance. Giannis Antetokounmpo draws so much attention when he attacks the rim that the Bucks are able to attain a steady diet of uncontested three-pointers coming off of passes from Giannis.
  • Miami being 29th in differential is interesting – they drop from 10th in the league all the way down to 16th. The Heat took shots in optimal areas, but weren’t able to create great looks from behind the arc. It will be interesting to if Jimmy Butler is able to change that dynamic this year.


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