Sports

NBA Defensive Player Rating is flawed

Numbers! How do they work, and why do they say that Nikola Jokić is better on defense than Joel Embiid?

Numbers! How do they work, and why do they say that Nikola Jokić is better on defense than Joel Embiid?
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Analytics can be misleading. Over the last decade, we’ve seen an influx of statistics take over the sports world, and basketball hasn’t been exempt from this revolution — just look at all the three-point attempts we see now across the NBA. But one stat in particular can be even dangerously misleading, and that is individual defensive ratings.

The whole idea of statistics has become so convoluted, I think we’ve gotten to the point where we just kind of take the analytics community’s word for it when they throw all these numbers at us. Defensive player rating would have us believe that Nikola Jokić is a better defender than Joel Embiid, and anyone with a pulse knows that isn’t true. Jokić isn’t a total liability defensively, but he’s no Embiid.

I’m not against advanced stats, but I don’t think they’re the end all be all of sports tracking. There should certainly be a balance between advanced stats and what’s actually happening on the field or court. To understand the defensive rating stat is to understand some of its absurdity when it comes to the individual player aspect of it.

This is how NBA.com’s stat glossary defines defensive player rating:

The number of points allowed per 100 possessions by a team. For a player, it is the number of points per 100 possessions that the team allows while that individual player is on the court.

Here’s another explanation courtesy of baskeball-reference.com:

The core of the Defensive Rating calculation is the concept of the individual Defensive Stop. Stops take into account the instances of a player ending an opposing possession that are tracked in the boxscore (blocks, steals, and defensive rebounds), in addition to an estimate for the number of forced turnovers and forced misses by the player which aren’t captured by steals and blocks.

Here is part of the actual formula used to calculate defensive player rating. This stat can’t be influenced by the defense of a player’s teammates:

Defensive Player Rating = (Players Steals*Blocks) + Opponents Differential= 1/5 of possessions – Times blown by + Deflections * OAPDW( Official Adjusted Players Defensive Withstand)

Anyone who understood that on the first go-around might be a genius. Anyone who can take this and justify Steph Curry having a better defensive rating than teammate Draymond Green at any point in their careers, then Mensa should be looking for you. Green is a former Defensive Player of the Year winner and, before his recent injury, was again in the running for the award. I don’t care what a statistician wants me to believe. I know what I see on the court, and it isn’t Curry being a better defender than Green. It’s not to diminish Steph, but that just isn’t the highlighted part of his game.

Whenever an announcer goes out of their way to tell me a player tries hard on defense, or he’s making more of an effort defensively, that’s just a nice way of saying, defense isn’t that player’s forte. Good examples of this are Curry and James Harden. Both players have a 106.8 career defensive rating. The NBA’s average defensive rating is 110.6. Compare this to a defender like Metta World Peace, aka Ron Artest, whose career rating is 103.4. According to this stat, Artest was barely a better defender than Curry or Harden. We know that isn’t true.

Of late, Luka Dončić has been on a roll, ranked third (93.9) in defensive rating over the last five games. The Mavericks have been better overall defensively than in past years, but I’m still not buying Luka as the third-best defender in the game even over a five-game period. But that is the nature of the defensive rating statistic. It’s one big gumbo of stats tossed together yet not nearly as satisfying to the palate.



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