BR Defensive Ratings????

[Reader]

How does Basketball Reference give Avery Bradley a defensive rating of 102 and James Harden a defensive rating of 96 for last nights game?

Does anyone know of a better site to check out specific game defensive ratings?

Thank you.

[deepak]

The formula for how individual DRTG is calculated is explained fully in the book Basketball on Paper, and is summarized here:

http://www.basketball-reference.com/about/ratings.html

You can see that about 80% of it is based on the team's defensive rating, and even the other 20% is largely based on team defensive statistics. So, the simple answer to your question is that for the game Houston had a team DRTG of 95 while Boston had a team DRTG of 108.

The theory behind DRTG is pretty solid, in my opinion, but for it to be somewhat reliable in a single game it needs more information that's not available in the boxscore like on-floor team stats. Incorporating counter-part statistics could also help refine the individual D component of the rating.

I think there are some folks who do defensive charting and publish DRTG's based on that for particular college teams. That would probably be the best way to go about it if you wanted really precise figures.

[Mike G]

So Avery Bradley was 6 points better than his team (108-102), while James Harden was 1 point worse than the Rockets as a whole (101-102).

This does suggest that Bradley was something like 7 points per 100 possessions better than James Harden, on defense.
But then James kicked Bradley's ass at the other end.

Whether you use plus-minus or team-tilted DRtg for a player, one game can't be assumed to be an accurate representation.

[andylarsen]

I wrote a post on this once:

http://www.slcdunk.com/2013/1/31/393935 ... ve-ratings

Basically: BR's DRTG is the Basketball on Paper DRtg, which works significantly better if you have the stats that Dean Oliver wishes for in his defensive outline. If you don't, the DRTG is essentially the team defensive rating, with a big adjustment for defensive rebounds and smaller adjustments for blocks and steals.

[Reader]

….. The theory behind DRTG is pretty solid, in my opinion, but for it to be somewhat reliable in a single game it needs more information that's not available in the boxscore like on-floor team stats. Incorporating counter-part statistics could also help refine the individual D component of the rating.

Thank you for the link Deepak. I share your viewpoint of the DRTG theory being pretty solid but it is not without it’s flaws, we are agreed upon that as well. I love the BR site and view it as indispensable but I just wish we had a better way to numerically capture defensive impact than the present ones available to us.

So Avery Bradley was 6 points better than his team (108-102), while James Harden was 1 point worse than the Rockets as a whole (101-102).

This does suggest that Bradley was something like 7 points per 100 possessions better than James Harden, on defense.
But then James kicked Bradley's ass at the other end.

Whether you use plus-minus or team-tilted DRtg for a player, one game can't be assumed to be an accurate representation.

Excellent point on how each player performed relative to their team’s performance but not sure what you mean when you say that the data suggests that, “James kicked Bradley’s ass on the other end.”

Also, I understand that one game cannot be expected to accurately reflect the entirety of a player but in this specific game, Bradley shut Harden down (33% shooting) without sending him to the line, Harden had 2 foul shots the entire game and he averages close to 10.

I wrote a post on this once:

http://www.slcdunk.com/2013/1/31/393935 ... ve-ratings

Basically: BR's DRTG is the Basketball on Paper DRtg, which works significantly better if you have the stats that Dean Oliver wishes for in his defensive outline. If you don't, the DRTG is essentially the team defensive rating, with a big adjustment for defensive rebounds and smaller adjustments for blocks and steals.

Great article Andy, thank you for sharing. These #’s certainly can lead to questionable conclusions at times.

[Mike G]

...not sure what you mean when you say that the data suggests that, “James kicked Bradley’s ass on the other end.”

Also, I understand that one game cannot be expected to accurately reflect the entirety of a player but in this specific game, Bradley shut Harden down (33% shooting) without sending him to the line, Harden had 2 foul shots the entire game and he averages close to 10.

I also have no idea what I meant. Either I didn't look at the boxscore, or I misread it. Sorry about that.

http://www.basketball-reference.com/box ... 30BOS.html
Harden's ORtg and DRtg are shown as 83-96, but his +/- was a reversal of that, at +12
Bradley was 118-102, but this too is counter-indicated by his +/- at -10