Rim Protection Adjustments and Revisions (more numbers)
After getting some positive offline feedback for Saturday's post, I realized that it really is a mistake to not adjust for pace and team factors when assigning credit to rim protection. For example, Chris Kaman's impressive (though small sample size riddled) numbers undoubtedly benefit from the fact that the Lakers allow the most shots at the rim in the league, and do so by a decent margin.
The average team allows around 28.6 shots at the rim per game, the Lakers currently allow 34.9, while the league leader in this category is Sacramento at 23.7 (more on this later), meaning that Kings bigs have more than 11 "opportunities" fewer per game to prevent points under the metric developed in the last post. Even considering that I'm trying to isolate rim protection from other factors of defense, not taking into account the prevelance or scarcity of these opportunities for a given player probably skews the results some.
So I made a simple adjustment to the data used in the original post. Essentially, I assumed that a league average big would challenge shots at the same ratio and efficiency regardless of the number of shots at the rim per game. Thus I was able to find the "expected" points saved/36 for each team based the degree and direction by which OFGA < 5ft were greater or lesser than league average. These adjustments changed the results to a degree as shown below (I've used data from games played up til last Friday to use the same sample as that in the original post:
So I made a simple adjustment to the data used in the original post. Essentially, I assumed that a league average big would challenge shots at the same ratio and efficiency regardless of the number of shots at the rim per game. Thus I was able to find the "expected" points saved/36 for each team based the degree and direction by which OFGA < 5ft were greater or lesser than league average. These adjustments changed the results to a degree as shown below (I've used data from games played up til last Friday to use the same sample as that in the original post:
Hopefully, this provides a little bit better idea of isolated rim protection by taking into account pace and perhaps capturing some deterrence value. Major problem with the adjustment is I've simply prorated the
"expected" number of contests based on the player's minutes and the team total - if I wanted to be more exact, I could attempt to use on/off data for each individual player, but then we get into further problems of 5 man units and the error inherent in the adjustment begins to swallow the data. As it stands, I'm pretty happy with this as a first pass at capturing rim protection in isolation from the publicly available data.
"expected" number of contests based on the player's minutes and the team total - if I wanted to be more exact, I could attempt to use on/off data for each individual player, but then we get into further problems of 5 man units and the error inherent in the adjustment begins to swallow the data. As it stands, I'm pretty happy with this as a first pass at capturing rim protection in isolation from the publicly available data.
A few quick notes:
- Given Indiana's stinginess in giving up shots at or near the rim, Hibbert looks even better than he did before the adjustment.
- One of the more surprising negative results, Marc Gasol, looks better in this data given Memphis' team data, but he still shows up as worse than average in terms of rim protection.
- Only one player (Amir Johnson) went from above to below average as a result of the adjustment and no players went from below to above.
- Lakers, Blazers and Jazz bigs got hammered a bit by the adjustment. That said, Robin Lopez still shows up really well, and given the Blazers scheme where he tends to get left on an island, he still has tremendous rim protection value (more on this in the upcoming days as well).
- Finally a note on the Kings - I don't think their low "shots at rim" defensive numbers actually represent good defense. They lead the league in personal fouls, which is certainly one way to prevent FGA at the rim, but not necessarily a good way since FTs are pretty high efficiency. The theory they foul to prevent layups is somewhat born out by their 3rd worst rank in OFG% on these shots, as shots taken while being fouled only count as attempts if the shot is made. More worryingly for them, they are bottom 5 in terms of most opponents 3's attempted and made and highest percentage of makes. This despite roughly league average pace. In other words, by "preventing" shots at the rim, they are giving up wide open looks from 3 and free throws, all of which goes to explain how they achieve their bottom 5 rank in Pts. Allowed/100.
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