If you follow the link you will hear Dan Patrick – now of Sports Illustrated – interview George Karl (hat tip to Andy Feinstein of Denver Stiffs – formally FireGeorgeKarl.com). In the course of this conversation Dan Patrick re-iterated a common critique of the Denver Nuggets: Denver doesn’t play defense.
Denver allowed 107 points per game, a mark that ranked 29th in a 30 team league. So it’s easy to see why people think Denver has problems on defense.
Denver is a “Good” Defensive Team
At least, it would be easy to see if you didn’t know one basic fact about basketball. Some teams play at a fast pace while others take it slow. This one basic fact means that to properly evaluate a team’s offense and defense we need to consider points scored and allowed per possession. In other words, we have to consider offensive efficiency and defensive efficiency.
The Nuggets average 103.1 possessions per game, which is the fastest pace in the NBA. Given this quantity of possessions, the Nuggets had a 103.7 defensive efficiency [(107.0 / 103.1)*100]. This mark ranks 12th in the 30 team NBA. In sum, Denver was actually an above average defensive team in 2007-08.
If you have read The Wages of Wins you have seen the argument that teams should be evaluated in terms of offensive and defensive efficiency. And such an argument is not unique to The Wages of Wins. It can be also found in the writings of John Hollinger and Dean Oliver. And I believe Oliver notes that this idea goes back decades. Yet apparently, it’s completely lost on Patrick.
Okay, Patrick is a sportswriter. Sometimes (as is often noted here), sportswriters get it wrong (see the vote for Kevin Durant for Rookies of the Year or Kobe Bryant for MVP). But what is truly amazing about the Patrick-Karl interview, is that after Patrick asserts that Denver is “bad” defensive team (where “bad” is defined as below average), Karl doesn’t disagree. One would think that Karl, who has to have heard that teams play at different speeds, would have quickly told Patrick that he was wrong. Once you adjust for pace, Denver is a “good” defensive team (where “good” is defined as above average). This, though, doesn’t happen. Is it possible that Karl doesn’t understand offensive and defensive efficiency?
Karl stated in the interview that Denver is beginning the process of preparing for next season. That process involves an evaluation of where this team is at, and what needs to be done to make it better. If you start such a process, though, with a distorted view of what is “good” and “bad”, it seems unlikely that you are going to end the process with an improved product.
Introducing the Distortion Score
To be fair to both Patrick and Karl, NBA observers do commonly refer to points score and allowed, rather than offensive and defensive efficiency. And as has been noted in many places (including The Wages of Wins), this common practice does distort our view of a team.
How much of a distortion do the common metrics create? To answer this question, I ranked each NBA team according to the following metrics:
- Points Allowed
- Points Scored
- Defensive Efficiency
- Offensive Efficiency
I then calculated the difference (labeled Defensive Difference) between the team’s defensive efficiency rank and its points allowed rank. Likewise, I also calculated the difference (labeled Offensive Difference) between the team’s offensive efficiency and points scored ranking. With these differences in hand, I calculated the team’s Distortion Score. This is determined as follows:
Distortion Score = Absolute Value of Defensive Difference + Absolute Value of Offensive Difference
The results for 2007-08 are reported in Table One
Table One: 2007-08 Distortion Score Rankings
As Table One reports, the team with the largest Distortion Score is the Denver Nuggets. As noted, the team is ranked 29th in points allowed but 12th in defensive efficiency. So Denver’s defense is very underrated. On offense it has the opposite problem. In terms of points scored the Nuggets rank 2nd in the league. In terms of offensive efficiency, though, the team is only ranked 11th. Yes, Denver is above average offensively. Just not as far above average as its points scored per game would suggest.
When we add together 17 (the Defensive Difference) and 9 (the Offensive Difference), we see a Distortion Score of 26. And as noted, this leads the league.
Denver, though, is not the only team whose performance is distorted by points score and points allowed. The Indiana Pacers ranked 26th in points allowed, but were 15th in defensive efficiency. On offensive, the Pacers ranked 7th in scoring per game, but 18th in offensive efficiency. So the standard metrics tell us that the Pacers were very good on offense and very bad on defense. The pace adjusted measures tell us that Indiana was actually a better defensive team .
Indiana was not the only team where the efficiency measures tell us the opposite story from what we see when we just look at scoring averages. Like Indiana, points scored and allowed tell us that Seattle and Charlotte were better on offense while the efficiency metric says the teams were stronger on defense.
For Portland, New Orleans, Dallas, Toronto, Washington, and Atlanta, we see the opposite story. These teams look like they are better on the defensive side of the ball. But when we look at team efficiency, we see that each of these teams is actually stronger on the offensive side of the ball.
Why this Matters?
The purpose of the Distortion Score is to highlight how much the traditional measures of points per game distort our assessment of individual teams. And by that measure, the view of Denver is the most distorted.
Let me close by noting again why all this is important. If a decision-maker wishes to improve an organization, the decision-maker must first know what is wrong. If your metrics, though, distort your strengths and weaknesses, then it really doesn’t help much.
For Denver fans, let’s hope that George Karl didn’t feel like correcting Dan Patrick on his show. If that isn’t the case, though, it looks like Denver’s efforts to improve this summer are off to a very bad start.
– DJ
Our research on the NBA was summarized HERE.
The Technical Notes at wagesofwins.com provides substantially more information on the published research behind Wins Produced and Win Score
Wins Produced, Win Score, and PAWSmin are also discussed in the following posts:
Simple Models of Player Performance
What Wins Produced Says and What It Does Not Say
Introducing PAWSmin — and a Defense of Box Score Statistics
Finally, A Guide to Evaluating Models contains useful hints on how to interpret and evaluate statistical models.
Wages of Wins Journal 
antonio
May 8, 2008
to be fair to Karl… i believe Hollinger (maybe not, but it was definitely a stat guy) said at the all-star break or half way through the season, something like that, the Nuggets were fourth in defensive efficiency, but payed terrible defense in the second half which is why they now stand at 12th in defensive efficiency. So maybe Karl was just referring to the recent play of the Nugget defense.
JTapp
May 8, 2008
Dean Oliver is supposedly working as a scout/statistician for the Nuggets, according to his website. I would certainly hope he’d have more influence.
It’s odd because George Karl is a UNC guy, and UNC is where this stuff supposedly originated, even before Dean Smith (and Smith used efficiency in his own analyses).
UNC’s Roy Williams, like Karl, agrees with similar criticism of his teams’ “poor” defense even though they often rank very highly in defensive efficiency. Maybe they go along with the criticism as a motivational technique?
John Middleton
May 8, 2008
I just wanted to say I appreciated this post. I love basketball and I work as a web analyst. This site just fuses those two together (basketball and analytics). Thanks!
Mountain
May 8, 2008
http://www.hoopsstats.com/basketball/fantasy/nba/denver-nuggets/team/stats/08/7/1-2-id
NBA opponent efficiency is not the same as defensive efficiency but it is easily available at hoopsstats.com by month and it shows for Denver they “allowed”(rounded)
Nov 112
Dec 117
Jan 120
Feb 117
Mar 127
Apr 132
That is a dramatic drop off larger than defensive efficency would show but the trend would be steadily down.
And in playoffs they did allow 115 pts a game.
So clearly they changed and weren’t a good defensive team at the end. The part that counts most. Karl and Patrick probably were focused on that part. And right to do so.
Brian
May 8, 2008
Football analysts share the same misconceptions. I continually hear comments along the lines of “keeping the opposing offense off the field,” usually associated with a preference for the running game which chews up clock time.
People don’t understand that sports like basketball (and football) are turn-based. No matter how hard you try or what you do, one team will always be within 1 possession of the other at all times.
There can be value to slowing the game down. A weaker team that can force fewer total possessions can tilt the outcome more towards randomness and based less on relative ability. But I don’t think analysts are referring to that concept. I think they really believe the “Peyton Manning can’t throw touchdowns from the sideline” fallacy.
Mountain
May 8, 2008
NBA opponent efficency is affected by pace so it does have the same issue discussed here and it isn’t a clear answer.
But Median NBA opponent efficiency was 113. Nuggets were 4th worst in league on this measure post all star game.
http://www.hoopsstats.com/basketball/fantasy/nba/opponentstats/08/1/eff/18-1
Still the best solution would be to compute pace adjusted defensive efficiency by month.
Mountain
May 8, 2008
Nuggets were fastest paced team but less than 10% faster than median. Just crude eyeballing it, looks like the Nuggets were better than average first 4 months but a bit below average in last 2.
Mountain
May 8, 2008
(I was adjusting those Nuggets monthly figures down by 10% and comparing to league median 113 to reach this summary description.)
A-ro
May 8, 2008
Perhaps George Karl is “ignorant like a fox.” If I were the coach, I would not discourage the idea that the team would be better if the players worked harder on defense. As long as he and the GM know the truth, who cares what he says to Dan Patrick?
Jason
May 8, 2008
I suspect very much that Karl and Roy Williams are aware of how good (or not good) their respective teams were on defense. I also suspect that for Karl, being a bit above average is, in his mind, not good. High standards may breed instances where anything short of superb becomes bad. Couple that with a decline in defense as the season progressed and not feeling the need to contradict Patrick and I think it’s quite likely that Karl could know that his team was better than average but still consider this bad.
Now if Denver comes back next year and walks the ball up the court to keep the score down thinking that this is synonymous with good defense, I’ll change the opinion, but I suspect that Karl’s comments are not insight into what he really thinks or what he’ll prioritize.
Huey
May 8, 2008
I created a visualization for this dataset at Many Eyes:
Huey
May 8, 2008
Oops, here’s the link:
http://services.alphaworks.ibm.com/manyeyes/view/S1p4mNsOtha6sSEV7IUmN2~
dustin
May 8, 2008
Random off-topic comment:
Win score is based off the box score, which by and large is an objective measurement of performance. Recently I read an interesting article on assist inflation. If this phenomenom is true (and I’m not saying it is), would this affect comparison’s of players between era’s?
link to article about this in college basketball:
http://www.basketballprospectus.com/article.php?articleid=14
Harold Almonte
May 8, 2008
Fast pacing is just a method some teams use to hide and make up some defensive possible holes. The objective is to translate all the forced misses of the game to the shooting gambling rather than to the defensive set. Not every team can do that all the time, it’s needed lot of athleticism, and ability to score a lot, and relatively efficient to take advantage of that (Phoenix).
The trap of fast pacing is that you also give to your opponent the posssibility to score a lot on you, but when you are able enough to be the SECOND team in all the league scoring points, you put a lot of stress on the opponent in order to be more efficient at scoring to beat you. But in the end those teams are victims of their defense when they can’t impose their pace, specially in a tired end of season.