The following table reports the regular season efficiency differential (offensive efficiency minus defensive efficiency) of the 37 teams that have won an NBA title since 1974.
Some quick observations from this table:
- these 37 title teams averaged a 6.5 efficiency differential and 59 regular season wins
- 15 team led the league in efficiency differential (offensive efficiency minus defensive efficiency) the year the team won the title
- 26 title teams ranked in the top three in efficiency differential
- No team has ranked 5th in efficiency differential and won the NBA title (that doesn’t really mean anything, but I thought I would toss that out there… and you will see in a moment which fans this observation might make angry)
- only 7 teams ranked outside the top four in efficiency differential have won a title (including the LA Lakers in 2009-10, whose mark of 4.9 ranked 7th in the league)
With these numbers in mind, let’s look at each team’s efficiency differential at the All-Star break in 2010-11.
Here are some interesting observations (at least interesting to me) from this table.
- The projected wins are not a forecast of where these teams will finish the 2010-11 season. This is simply the number of wins the corresponding efficiency differential typically translates into across an 82 game season. Efficiency differential explains about 95% of team wins and is considered a better measure of a team’s future prospects.
- The top three in efficiency differential this season are the Miami Heat, San Antonio Spurs, and Boston Celtics.
- The Lakers have improved since last year.
- But the Lakers currently rank 5th in efficiency differential.
- The Dallas Mavericks have the 4th best winning percentage in the NBA. But their efficiency differential suggests this team is not a title contender. And I am not sure a healthy Dirk Nowitzki is enough to close the gap.
To illustrate, let’s move from efficiency differential to Wins Produced for the Dallas Mavericks.
The table above indicates that the Mavericks are led this season by Jason Kidd and a healthy Tyson Chandler. Dallas did recently struggle without Nowitzki, but look at the productivity of Brian Cardinal (a player who got more minutes when Nowitzki was out).
The performance of the Mavericks this season is consistent with a team that will win about 51 games across an 82 game season. Dallas has already won 40 games (about six more than their efficiency differential suggests). So they will probably win more than 51 games. But teams with a differential below 4.0 don’t typically win NBA titles.
Then again, teams that are this bad do win more often than the team that ranks 5th in efficiency differential. So maybe fans of Dallas should be more optimistic than fans of the Lakers (then again, maybe not).
– DJ
P.S. Arturo Galletti has done far more than my simple post in exploring which teams are contenders (or pretenders). Following this link to just one of his recent stories on this subject.
Wages of Wins Journal 
Italian Stallion
February 21, 2011
Since Dallas performed so poorly while Dirk was out, wouldn’t it make some sense to calculate their efficiency differential for just the games Dirk played to see the difference and range?
I might even exclude a couple just after he returned because he was hobbling around the first week or so.
The straight point differential for the 9 game stretch he missed not adjusted for home/away, pace, or schedule was -5.89 over the 9 games. That’s pretty dreadful and has to have had an impact on the overall rating.
In the next game he played limited minutes and they lost by 19.
Granted, every team has had some injuries, they are all built into the team differentials, and it’s hard to isolate Dirk’s impact, but going 2-8 while Dirk was out or limited and 38-8 while he was playing suggests Dallas is a lot better when Dirk is healthy.
I’d tweak expectations for Dallas up going forward relative to the average.
Matt
February 22, 2011
Discussing the fact that no team has won a title with the 5th ranked efficiency differential was the single most useless point I’ve ever seen conveyed on this site.
I thought what made this site different was intelligent statistical discussion. Baiting a fanbase with a meaningless point is bush league.
Nerd Numbers
February 22, 2011
Matt,
Ima put on my bouncer hat (thanks Mosi) and say your comment is out of line. DJ pointed out the fact that the 5th ranked was just a fun jab at why LA can’t win. Second, you can’t exactly use the “don’t bait by being bush league” when you’ve done the same.
Why would I reply if I think you’re just trying to evoke a response. Because I get to use one of my favorite lines of all time! Matt, you need to watch more games. Commentators pull meaningless and trivial stats all the time to show why a team is good. E.g. “This team has the most offensive rebounds on weekends. The last team with more than 6.0 offensive boards on the weekends was the 1996 Chicago Bulls. Not bad company to be in.”
Anyway, when you want to get back to intelligent statistical discussion let me know, I’ve got tons of thoughts on the subject.
Mo
February 22, 2011
Lakers fans should be optimistic. This tells me that a team that’s 5th in efficiency differential is due to win a championship.
/gambler’s fallacy
AOM
March 12, 2011
I have a good handle on offensive efficiency and how it is calculated. But, how exactly do you calculate deffensive efficiency? More specifically, I assume that points allowed is the numerator. For the denominator – do you use the same possessions as is used in the offensive calculation? Should you use a possession calculation for the opponents’ possessions (i.e. use opponents’ FGA, FTA, TOs, etc.)? Something different? You could get slightly different outcomes depending on how you think about the denominator. Any thoughts?