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View Full Version : Stat heads; DRtg V Def Eff



Gander13SM
01-13-2016, 05:35 PM
Can anyone explain to me the difference in how these are measured? All I can find on them is "the number of points a team allows per 100 possessions." ...but I can't work out what one is measuring that the other isn't. They can't be measuring the same thing the exact same way because the results are very different.

Anyone?

Gander13SM
01-13-2016, 05:36 PM
Also is one regarded as more "respected" then the other? I've always used DRTG but I'm now being told def eff is the better stat... but I can't see why.

Quinnsanity
01-14-2016, 07:22 PM
Defensive efficiency is a rating of how many points a team allows per 100 possessions. To simplify that, it divides points allowed by total possessions and multiplies it by 100.

DRtg, or defensive rating, measures the same thing and CAN be used interchangeably with defensive efficiency for teams, but when people use DRtg they tend to be referring to it for an individual player. That measures how many points a team allows per 100 possessions when that player is on the floor. Of course, this number is largely useless without context, but if you know what a team's number is you can compare it to the player's to see if the team's defense gets better or worse when that player is on the floor. Be very careful about where you get DRtg numbers for individuals, though. There are some great stat sites, Basketball Reference being the main culprit, that uses individual DRtg not as an actual measure of points a team allows per 100 when someone is on the floor, but as an estimate of how many points a player gives up per 100 (it's a bit more complicated than that, but the point is those numbers are largely useless because they're estimates). The best place to go for per 100 numbers, on/off numbers, lineup stats, really anything of that ilk, is the NBA.com stats page. The Hollinger stats ESPN has for teams are very good as well, but they aren't as thorough or clear with individuals.

The same applies to offensive efficiency and ORtg, though ORtg is rarely used in discussion of individual players. Hope this helps.

Chronz
01-14-2016, 08:12 PM
I think hes talking about the differences in the formula between both barometers, it basically comes down to how they define possessions. IIRC BBR estimates while NBA calculates them completely. Could be wrong but its usually not much of a difference in terms of rankings

DODGERS&LAKERS
01-15-2016, 03:49 AM
I hate that Bball reference uses D rtg, and uses it as a factor in calculating win shares and ws/48. Its a team accomplishment. Drtg without context would have you believe Boozer is a superior defender to CP3.

PatsSoxKnicks
01-15-2016, 11:09 PM
I think hes talking about the differences in the formula between both barometers, it basically comes down to how they define possessions. IIRC BBR estimates while NBA calculates them completely. Could be wrong but its usually not much of a difference in terms of rankings

I'm 99% sure NBA estimates possessions too- at least for teams. The ones on Nylon Calculus are exact possession counts- probably the best to use.

IndyRealist
01-16-2016, 12:29 AM
I hate that Bball reference uses D rtg, and uses it as a factor in calculating win shares and ws/48. Its a team accomplishment. Drtg without context would have you believe Boozer is a superior defender to CP3.

DRtg was never meant to be used without context. It's not really the fault of the site or the stat, it's the fault of the people who don't understand it.

Quinnsanity
01-16-2016, 03:26 AM
I'm 99% sure NBA estimates possessions too- at least for teams. The ones on Nylon Calculus are exact possession counts- probably the best to use.


IIRC the NBA uses estimates but the margin of error is relatively minor. I took a class taught by the head of NBA analytics and I vaguely remember that being the case but don't quote me on it. But yes, if Nylon has exact possession counts those would be the best numbers to use.

PatsSoxKnicks
01-16-2016, 03:37 AM
IIRC the NBA uses estimates but the margin of error is relatively minor. I took a class taught by the head of NBA analytics and I vaguely remember that being the case but don't quote me on it. But yes, if Nylon has exact possession counts those would be the best numbers to use.

That's probably true. But we had this discussion and I'm fairly certain someone with NBA.com confirmed they use estimates, otherwise Nylon wouldn't have bothered calculating exact possession counts themselves (and I am 100% Nylon does display exact possession counts). In fact, I believe someone figured out their exact calculation.

There was also a recent article that looked into that on the site.

Gander13SM
01-16-2016, 01:22 PM
Thanks for all the info. And yes it was more about how they were being calculated.

For example I noticed Hollinger has;

Warriors 4th.
Miami 6th.
Detroit 8th.

While BBallRefs DRtg has;

Warriors 5th.
Miami 8th.
Detroit 6th.

Seemed odd.

Guess I'll stick Hollinger or the official nba page from now on. Thanks again guys.

DODGERS&LAKERS
01-16-2016, 02:25 PM
DRtg was never meant to be used without context. It's not really the fault of the site or the stat, it's the fault of the people who don't understand it.

That is somewhat true. But you know far too often people will list that as reasoning for one player being a better defender than another. Also, win shares and win shares / 48 get touted a lot without people knowing that the flawed defensive rating stat is heavily influential on them.