Defensive rating (DRtg) How you calculate it and use it

[fpliii]

to be honest, I think it might be better to find the z-score of defensive rating (# of standard deviations from league average that season)

maybe I'll put together a spreadsheet and upload it

[magictricked]

I don't have any problem with adjusting for league average, but wouldn't you also have to adjust for league average on the offensive side of the ball as well?

The consensus from the guys with the Bulls icons is that you just can't compare the defensive stats across eras for some inane reason. If that is true then you also can't compare offensive stats across eras. You can't just keep the inflated offensive stats and ignore the weak defensive stats because it doesn't match the mythology you are familiar with.

You cannot use defensive rating OR offensive rating to go from year to year without serious adjusting for league averages, Neil Paine has a post on his Basketball reference website about how it's done, it's not easy but without doing it anybody who tries to compare years is just blowing smoke. You may as well just make up numbers out of thin air because that's about as accurate as it is

[Yao Ming's Foot]

If I've understood the definition of terms correctly, this methodology treats an opponent with a defensive rating of 106 in a year where the league rating is 108 as an equally tough defensive opponent as a team with a defensive rating of 100 in a year that the league average was 102. This is clearly not the case. I've only really looked at players in the mold of high-usage perimeter scorers, but those guys absolutely FEAST on defenses with ratings greater than 106 and even the greatest have struggles against the teams with ratings less than 100.

For this reason, when I was originally having a look at this topic I decided not to assess the opposing team defense against the league average, but rather use the raw defensive ratings. Why? I think you need to directly assess the statistical productivity of a player in the statistical environment in which it was produced, and that environment has fluctuated significantly between 1991 and 2010.

If we look at a player's Offensive rating as a return on investment, then a 10% return on investment is much more valuable during the lean times of the Global Financial Crisis than during periods of economic prosperity. And for NBA scoring efficiency, 1999-2004 was the Global Financial Crisis.

During Jordan's first 3-peat the yearwise league average ORtg/Drtg was around 108 in the regular season and 110 in the playoffs. Scoring was cash money, and MJ logged around a 32% of both his career playoff games and minutes during this span. Things remained fairly fruitful in the next 5 seasons, with a yearly average rating of 106.8 in the regular season and 107.1 during the playoffs. MJ played approximately another 38% of his career playoff games and minutes during this stretch.

From the start of the Tim Duncan championship season in 1999 to the End of the Shaq/Kobe Lakers era in 2004 the yearwise league rating was 103.4 in the regular season and 103.0 in the playoffs. You might as well have hid your money under the mattress, because times were tough. These 6 years were the 6 lowest for ORating/DRating in the last 20 regular seasons and included the lowest 5 for the last 20 playoff seasons. Duncan played around 43% of his career playoff games during this stretch and 45.47% of his total playoff minutes, Shaq around 46.7% (51.5% of minutes) and Kobe 52% (and 56% of his total playoff minutes).

Since then things have picked up again with average ratings of 106.2 regular season and 107.0 playoffs from 2005-2007 and 107.8 regular season and 108 playoffs from 2008-yesterday. Obviously the modern era of stars like Dwade, LeBron and Chris Paul have played all or nearly all of their playoff games during these years when the points are flowing freely again.

I really want to write a detailed analysis in full when I find the time, but consider this brief breakdown of the best and worst opponent defenses for just Jordan, Wade, LeBron and Kobe. (These include series prior to 91 and were compiled before the 2010 playoffs, so slightly out of date).

These 4 guys have played a series against an opponent with a defensive rating better than 102 on 27 occasions in their careers:
3 times for Jordan - 3 series wins against 93 NY, 97 MIA, 98 IND, includes No Finals, 1 series against ratings better than 100
3 times for Wade - 3 series losses against 04 IND, 05 DET, 07 CHI, includes No Finals, 2 series against ratings better than 100
3 times for LeBron - 3 series losses against 07 SA, 08 BOS, 09 ORL, includes 1 Finals, 2 series against ratings better than 100
18 times for Kobe - 14 series wins, 4 series losses, includes 5 Finals, 13 series against ratings better than 100 including 4 Finals

These 4 guys have played a series against an opponent with a defensive rating worse than 106 on 29 occasions in their careers:
16 times for Jordan - Includes 1 Finals (2 other Finals in the 105s, 2 more in the 104s), 6 series against rating worse than 108
2 times for Wade - Includes 0 Finals (06 DAL at 105), No series against rating worse than 108
6 times for LeBron - Includes 0 Finals, 3 series against ratings worse than 108
5 times for Kobe - Includes 0 Finals, No series against ratings worse than 108

You can't look at raw defensive ratings w/o regard to the league average, because it completely ignores rule changes, changes in playing styles, etc. that have occurred over time. For instance, our best estimate of the league average defensive rating in 1958 was 89.1. By your logic, that means every team in the NBA that year was significantly better defensively than the best defenses of the past 25 years! But we know that's not necessarily true -- it's just the way the game was played back then, the strategy was to run down the court as quickly as possible and jack up the first shot you could get (pace factor in 1958: 118.9!!). If we compare to the league average, we still see that the 1958 Celtics (DRtg: 84.9) were a good defensive team, but they were more like a team with a 103 DRtg in today's game, not a team with an 85 DRtg.

Now, it's true that a DRtg of 100 in a league where avg = 102 is slightly more valuable than a DRtg of 106 where avg = 108, simply because when the scoring environment is lower, 2 points of efficiency differential is more valuable. So we could plug the numbers into the pythagorean formula and come up with a slightly more accurate read on the relative value of defense. But you still have to compare to the league average somehow.

Neil,

I think there are many situations when comparing to the league average is necessary. The example you presented of determining how fundamentally "good" a defense is between years and eras is one of them. There it is particularly important to understand the effect of rule changes, the 3-point line, pace, style of play etc. That is, how well was a team able to work within the confines of the prevailing environment to produce statistically tough defense.

My logic does not assume that a lower team defensive rating means a "better" defensive team. My logic assumes that a lower team defensive rating means that the team has demonstrated over the course of the regular season that it more difficult for the opposing players to score a high number of points per possession against them than a team with a worse defensive rating. This is regardless of the year,era or league average rating of the two teams. We should statistically evaluate how a player actually does perform offensively directly against the statistical standard of defense.

I don't think the 1958 Celtics (DRtg 84.9) defenses are fundamentally better defensively than the 2008 Celtics (DRtg 98.9). Even if the two teams had a DRtg an equal number of points below league average DRtg for their season I'm still not judging Bob Pettit for shooting 42.3% on field goals (and whatever his corresponding ORtg would have been) in the 1958 Finals series against Boston as harshly as I would judge Kobe for shooting 40.5% or LeBron for shooting 35.5% in their respective playoff series against the 2008 Celtics.

I'm willing to be convinced otherwise, but I don't think that 'points better than league average' is an appropriate comparative measure of how tough it is to produce numbers against teams with low defensive ratings. People say defense was much tougher during the 1990's hand-check era, and physically it probably was. But is that toughness reflected in the Defensive ratings of the top teams of the era?

Don't worry Anon, I'm not trying to stir up anything against Jordan. To me he is the best player that has ever played the game, at least that's what the Jordan memorabilia plastered all over my walls seem to reflect.

Looks like not every Jordan fan lives their life with their head in the sand.



http://www.basketball-reference.com/blog/?p=6142

[magictricked]

Looks like not every Jordan fan lives their life with their head in the sand.



http://www.basketball-reference.com/blog/?p=6142

You're just reading things you want to read.

the first post you quoted, the big long one is a non stat guy trying to argue (and failing) you don't have to adjust the stat to go across eras.

the second post you quoted is stat guru Neil Paine the owner of Basketball
Reference telling him he's full of sh*t...lol Which is what several people including me have been saying in this thread

That's why since this three year old conversation on basketball reference you dug up there is a formula for adjusting the ratings from year to year

You can't look at raw defensive ratings w/o regard to the league average, because it completely ignores rule changes, changes in playing styles, etc. that have occurred over time.

[Yao Ming's Foot]

You cannot use defensive rating OR offensive rating to go from year to year without serious adjusting for league averages, Neil Paine has a post on his Basketball reference website about how it's done, it's not easy but without doing it anybody who tries to compare years is just blowing smoke. You may as well just make up numbers out of thin air because that's about as accurate as it is

Once again I'm not ranking defensive teams I'm ranking the strength of offensive performances against them.

It only makes sense to include the league average if you also factor in the league average on the offensive numbers as well.

What's more impressive hitting 3 HRs off of league average pitching during the steroid era of baseball or hitting 3 HRs off of league average pitching during the dead ball era of baseball?

[Yao Ming's Foot]

You're just reading things you want to read.

the first post the big long one is a non stat guy trying to argue you don't have to adjust the stat to go across eras.

the second post is stat guru Neil Paine the owner of Basketball
Reference telling him he's full of sh*t...lol Which is what several people including me have been saying in this thread

That's why since this three year old conversation on basketball reference you dug up there is a formula for adjusting the ratings from year to year

Did you notice he never responded after that? Neil Paine thinks the point is to measure what defense is better. It's not. The point is how to compare the offensive performances against those defenses.

Imagine two identically great offensive performances. Both of them were against league average defenses. However the league during one of them was offensive friendly leaguewide. Scores and efficiency numbers were off of the charts. The league during the second game was notorious for being defensive friendly. Scoring and efficiency numbers were way down . Are you telling me that since they were both against league average defenses that they would be equivalent performances despite that?

[DatAsh]

to be honest, I think it might be better to find the z-score of defensive rating (# of standard deviations from league average that season)

maybe I'll put together a spreadsheet and upload it

I'd very much be interested in seeing how those results turn out.


YaoMingsFoot,

You really need to give the cross era defensive ratings comparison a rest. That being said, the agenda you're trying to push, that Kobe's faced tougher defenses than Jordan in the finals probably has some truth to it. Kobe's had some pretty tough defensive opponents in the finals(Celtics twice, Pistons).

Your agenda would be better laid arguing from a non statistical stand point. I even think you might get some respectable posters to agree with you and back you up, but no respectable poster is going to agree that Jordan's Wizards were a better defensive team than Jordan's Bulls.

[KG215]

to be honest, I think it might be better to find the z-score of defensive rating (# of standard deviations from league average that season)

maybe I'll put together a spreadsheet and upload it

Math major from Stanford, right? Please do.

I'm not saying Yao Ming's Foot is wrong for using DRtg. I just think the way he uses it is misleading.

[Yao Ming's Foot]

I'd very much be interested in seeing how those results turn out.


YaoMingsFoot,

You really need to give the cross era defensive ratings comparison a rest. That being said, the agenda you're trying to push, that Kobe's faced tougher defenses than Jordan in the finals probably has some truth to it. Kobe's had some pretty tough defensive opponents in the finals(Celtics twice, Pistons).

Your agenda would be better laid arguing from a non statistical stand point. I even think you might get some respectable posters to agree with you and back you up, but no respectable poster is going to agree that Jordan's Wizards were a better defensive team than Jordan's Bulls.

Of course it has some truth to it. It couldn't be more obvious. I'd probably like to throw out all stats too if I had absolutely none on my side that put the Jordan's finals opponents even in the conversation.

I'm still waiting for somebody to tell me that putting up numbers against a league average defense during an era of basketball where everyone is scoring in bunches is equally as impressive as putting up numbers against a league average defense where everybody is struggling to score efficiently. That's what you guys believe right?

[KG215]

Of course it has some truth to it. It couldn't be more obvious. I'd probably like to throw out all stats too if I had absolutely none on my side that put the Jordan's finals opponents even in the conversation.

I'm still waiting for somebody to tell me that putting up numbers against a league average defense during an era of basketball where everyone is scoring in bunches is equally as impressive as putting up numbers against a league average defense where everybody is struggling to score efficiently. That's what you guys believe right?

I'm curious, between Kobe and Jordan, who do you think is the better scorer?

Look at Jordan's insane scoring seasons in the '80s and '90s.

1986-1987: Jordan 37.1 ppg on .484 FG%, .562 TS%, .484 eFG%; league average DRtg was 108.3

1987-1988: Jordan 35.0 ppg on .535 FG%, .603 TS%, .507 eFG%; league average DRtg was 108.0

1988-1989: Jordan 32.5 ppg on .538 FG%, .614 TS%, .546 eFG%; league average DRtg was 107.8

1989-1990: Jordan 33.6 ppg on .526 FG%, .606 TS%, .550 eFG%; league average DRtg 108.1

I could go all the way through '93 when he still averaged 31, 30, an 32 PPG on similar percentages against similar DRatings, but you get the point.



Compare that to Kobe's two big breakout scoring seasons in '05-'06 and '06-'07.

2005-2006: 35.4 ppg on .450 FG%, .559 TS%, .491 eFG%; league average DRtg was 106.2

2006-2007: 31.6 ppg on on .463 FG%, .580 TS%, .502 eFG%; league average DRtg was 106.5


I know the league average DRtg was higher in Jordan's era but I'm guessing that 1-2 point difference doesn't mean a whole lot. I'm just wanting to see where, exactly, you're coming from. I agree, some of the defense Kobe faced in the Finals were better than some of the teams Jordan faced in the Finals. I'm just curious whether or not you think Kobe is the better scorer between the two.

[Yao Ming's Foot]

I'm curious, between Kobe and Jordan, who do you think is the better scorer?

Look at Jordan's insane scoring seasons in the '80s and '90s.

1986-1987: Jordan 37.1 ppg on .484 FG%, .562 TS%, .484 eFG%; league average DRtg was 108.3

1987-1988: Jordan 35.0 ppg on .535 FG%, .603 TS%, .507 eFG%; league average DRtg was 108.0

1988-1989: Jordan 32.5 ppg on .538 FG%, .614 TS%, .546 eFG%; league average DRtg was 107.8

1989-1990: Jordan 33.6 ppg on .526 FG%, .606 TS%, .550 eFG%; league average DRtg 108.1

I could go all the way through '93 when he still averaged 31, 30, an 32 PPG on similar percentages against similar DRatings, but you get the point.



Compare that to Kobe's two big breakout scoring seasons in '05-'06 and '06-'07.

2005-2006: 35.4 ppg on .450 FG%, .559 TS%, .491 eFG%; league average DRtg was 106.2

2006-2007: 31.6 ppg on on .463 FG%, .580 TS%, .502 eFG%; league average DRtg was 106.5


I know the league average DRtg was higher in Jordan's era but I'm guessing that 1-2 point difference doesn't mean a whole lot. I'm just wanting to see where, exactly, you're coming from. I agree, some of the defense Kobe faced in the Finals were better than some of the teams Jordan faced in the Finals. I'm just curious whether or not you think Kobe is the better scorer between the two.

They look pretty comparable to me. I think Jordan would have the edge in regular season scoring though. I don't think thats a myth by any means.

The mythology is that Jordan was unstoppable. That he would just crush the 04 Pistons. The 08 Celtics would have been toast. When in fact the two times he faced a couple of sub 100 defensive rated teams (Heat and Knicks) he was a sub 40% shooter. The one time he faced what I consider a comparable Kobe defense in the Finals (the Sonics) he put up his worst numbers. The mythology is that any time Kobe struggled, Jordan would not have. That since it was the Finals all the buckets were falling and not because it was the Suns or the Jazz or the Lakers or whatever defensive team would barely rate as average in terms of limiting efficient scoring in in Kobe's world.

[DatAsh]

Of course it has some truth to it. It couldn't be more obvious. I'd probably like to throw out all stats too if I had absolutely none on my side that put the Jordan's finals opponents even in the conversation.

Can't say that I really disagree with you here, but I think you may have me confused for someone else.

I'm not arguing for Jordan, you ard I are in agreement with the fact that Kobe's finals opponents have been tougher defensively; I'm arguing against trying to compare defensive ratings across eras, and telling you why it's not as valid as you might think.

If you want to show that Kobe's generally faced tougher finals defenses, list the opponents that each of the two player's has played against and go in depth as to why you feel Kobe's opponents were superior. I think most unbiased fans on this sight here will agree with you.

Don't try to use a statistic that shows the Jordan Wizards were better than the Jordan Bulls, and that virtually all of the best defensive teams ever come from the 50s and 60s. That won't gain you any credibility, and it will ultimately lead the topic off on a tangential debate concerning the credibility of the stat itself, as it has done virtually every other time.

[fpliii]

I'd very much be interested in seeing how those results turn out.


YaoMingsFoot,

You really need to give the cross era defensive ratings comparison a rest. That being said, the agenda you're trying to push, that Kobe's faced tougher defenses than Jordan in the finals probably has some truth to it. Kobe's had some pretty tough defensive opponents in the finals(Celtics twice, Pistons).

Your agenda would be better laid arguing from a non statistical stand point. I even think you might get some respectable posters to agree with you and back you up, but no respectable poster is going to agree that Jordan's Wizards were a better defensive team than Jordan's Bulls.

Math major from Stanford, right? Please do.

I'm not saying Yao Ming's Foot is wrong for using DRtg. I just think the way he uses it is misleading.

https://docs.google.com/spreadsheet/...m51NkZ2UU1sSlE

there's probably a quicker way to do this, but I'm updating year-by-year

if there's a season in particular you want me to skip ahead to, let me know

notes: seasons prior to those listed on BBR use elgee's method (his site is http://backpicks.com), which gives a very close estimate:

http://www.backpicks.com/2012/04/18/...and-much-more/

the average error is quite low, and it's the best estimator we currently have

[magictricked]

Did you notice he never responded after that? Neil Paine thinks the point is to measure what defense is better. It's not. The point is how to compare the offensive performances against those defenses.

Probably because he's not going to spend all night arguing with idots

the rest, just stop talking. You calling out Paine for not knowing how to use a stat is hilarious. you're the one who's using it wrong. Instead of arguing you should open your mind and try and learn something. Instead all you've done is deny the elephant in the room is an elephant. It's ok to be ignorant on a subject as long as you use it to learn. You refuse to learn from people trying to teach you something and that makes you stupid.

And like Neil Paine, i'm done talking to the idiot.

[KG215]

https://docs.google.com/spreadsheet/...m51NkZ2UU1sSlE

there's probably a quicker way to do this, but I'm updating year-by-year

if there's a season in particular you want me to skip ahead to, let me know

notes: seasons prior to those listed on BBR use elgee's method (his site is http://backpicks.com), which gives a very close estimate:

http://www.backpicks.com/2012/04/18/...and-much-more/

the average error is quite low, and it's the best estimator we currently have

Looks good to me, but I'm not going to pretend to understand it haha. You'll have to explain to me what the z-score is and how you calculate it. I'm guessing you just add it to the original ORtg or DRtg?