On the court versus off the court



Change between on-court and off-court values

The above chart illustrates the change in the Houston Rockets offensive and defensive ratings with and without each player on the floor. The numbers represent the difference between on court and off court values for each player. For the sake of making it more intuitive, I flipped the defensive rating so positive numbers indicate better performance and negative numbers indicate worse performance. So, if we take Chandler Parsons, the Rockets average 6.3 more points for 100 offensive possessions with him on the floor, but opponents average 4.4 more points per 100 defensive possessions.

Starters = offense, bench = defense

Generally speaking, the starters seem to add offensive value while the bench players seem to add defensive value. Harden leads the way with an extra 9.4 pp100, while on defense Donatas Motiejunas surprisingly is on top with 7.4 pp100.

Two things should be pointed out before conclusions are reached. The first is that these values are not absolute, they’re relative. In other words, it’s a comparison between a player and the his bench/starter replacement. This might explain why Dwight Howard’s defensive value is basically neutral, because his backup, Omer Asik, is very good defensively.

Second, strength of opposing needs to be considered, as bench players are typically matched up against other bench players. So we need to add a layer of relativism. Each value is therefore relative to the player’s replacement and the player’s opponents.

What’s with Terrence Jones and Parsons?

All those disclaimers aside, some values definitely jump off the page. Most striking, at least to me, is that Jones and Parsons are terrible defensively. While the other starters are pretty much neutral defensively (above disclaimers considered), Parsons and Jones are -4.4 and -6, respectively. Because they’re so bad, their immediate backups (Jordan Hamilton and DMo) look amazing comparatively, at 4.3 and 7.4, respectively.

While the disclaimers matter, they matter less in these cases. The other starters are playing against the same opponents as Parsons and Jones, but do not have such bad defensive values. The other bench players, who play against the same opponents as DMo and Hamilton, do not have such good defensive values. Also, it’s not like DMo and company are necessarily renowned for their defensive prowess. Something is happening here. Is it possible that Parsons and Jones are the weak links in the Rockets defense?

About the author: Richard Li is an independent researcher and consultant. He likes numbers and pictures.

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