We argue about this all the time and really without much real evidence to support the notion that a coach always makes a significant impact. For me it's mostly about the talent, but I decided to look into it and see what research there is and what it suggests. For all those whining about who the next coach is and being in an uproar that Rambis could be the Coach buckle up and read this.
In a league where coaching turnover is rampant—almost eight changes per season over the past two decades—a study co-written by Southern Utah University economics professor Dave Berri suggests that fewer than a quarter of NBA coaches between 1977 and 2008 had any significant effect on their players' performance.Mr. Berri looked at 62 coaches in the three-decade span, only including those who worked long enough to have 15 everyday players come to their team after their arrival, as well as 15 everyday players leave (this was to make sure each coach had a sizable roster of players to analyze). Mr. Berri used his wins-produced metric—which shows how many wins a player is worth by seeing how his statistics correlate to winning—to measure the players' performances and see whether they significantly improved or declined. If they did, then the coach passed the so-called effectiveness test.
Phil Jackson, who has won a record 11 titles, is worth 17.1 wins to his teams per year according to this metric—the most in the sample. But Hall of Famer Pat Riley had no significant effect at all; neither did well-known coaches such as Jeff Van Gundy and Jerry Sloan. Then there's Matt Guokas, who compiled a .430 winning percentage in seven years as head coach. He's the only person in this sample to make his players significantly worse.
http://www.wsj.com/articles/SB10001424052748703506904575592363492225220Coaches or Players?It is these two perspectives that inspired a study conducted by Michael Leeds, Eva Marikova Leeds, Michael Mondello, and myself. Utilizing data from the NBA, we wished to see if coaches can actually impact the performance of the players. Specifically, we wished to know if a statistical relationship existed between player performance in the NBA and the identity of the player’s coach.
Our work has been detailed in an unpublished paper (that is currently under review at refereed journal). This work will also be detailed in our forthcoming book [Stumbling on Wins from Wharton School Publishing/Financial Times Press].
Normally I don’t go out of my way to discuss my unpublished papers in the forum. And I have definitely gone out of my way to avoid discussing the many new stories we plan for the next book.
But a few weeks ago I got a call from Ryan McCarthy. Ryan was working on a story for Slate.com looking at the value of NBA coaches. Given where we are at in writing the book, I thought I would share our basic findings.
From McCarthy’s article you get the general story. Here are a few excerpts (click on the previous link for the entire article, which is well worth reading):
According to a new study co-authored David Berri, an economist who runs the sports blog Wages of Wins, most NBA coaches are similar to company managers. In the study, Berri and his colleagues sought to investigate whether Adam Smith’s theory that workers make up the value of an organization-and that managers are nothing more than “principal clerks“-applies to the NBA. The economists looked at a group of 19 longtime NBA coaches that had helmed multiple teams, using a Bill Jamesian statistic called Win Score to evaluate how players performed under their tutelage. Only eight of the 19 coaches had any statistically discernible effect on team performance. Seven had a positive impact, with Phil Jackson topping the chart. Next on the list: Rick Adelman, Rudy Tomjanovich, Rick Carlisle, Don Nelson, Flip Saunders, and Gregg Popovich. The only coach who had a demonstrably negative impact on his players: the historically inept Tim Floyd. (For what it’s worth, Berri didn’t study Isiah Thomas. The NBA coaches study hasn’t been published yet; a version of it will be included in the 2009 book Stumbling on Wins, by Berri and Martin Schmidt.)
More interesting than the names on Berri’s list is his finding that the influence of even the best coaches was statistically very small and was distinguishable only from the worst-rated coaches, like Floyd. Even title-winning, Hall of Fame coaches like Pat Riley and Larry Brown were shown to have almost no impact on their teams. Players leaving Riley-led teams actually got better (except, it seems, for Antoine Walker).
And here is how McCarthy’s article ends:
Why is it that, in the NBA, inexperienced coaches can step in and succeed right away? (First-time coach Avery Johnson was named the NBA’s coach of the year in his second season on the job; newbie Doc Rivers won it after his first.) Berri’s contention is that an NBA coach’s record is determined almost entirely by the quality of his players. The claim makes sense: In comparison with football and baseball, NBA statistics vary little from year to year. The job of an NBA coach, then, may be less about coaxing better performances out of athletes than about getting their skills and personalities to fit together. By the time a player has moved through the basketball machine to the NBA, he’s a relatively finished product. Despite Mike D’Antoni’s best efforts, the plodding center Eddy Curry is doomed to be himself. “Think about it,” says Berri. “What is a coach going to say that will get Eddy Curry to rebound?”
Let me summarize: The majority of the coaches we looked at did not have a statistically significant impact on player performance. And some of these coaches are ranked among the all-time greats. Such findings suggest that the outcomes we observe for teams are mostly about the players, not the coaches. So teams that wish to improve should focus on the people in the uniforms, not the people wearing suits on the sidelines.
What does this mean? Certainly I suspect the coaches in the NBA know much more than the “idiots” – or deck chairs – in the stands. Our study, though, did not explore these differences. What we did try and do is explore the differences in NBA coaches. And our study found that in many cases, there were not any substantial differences. In sum, although one has to acquire substantial knowledge to be an NBA coach, there isn’t much one of these coaches is able to do to differentiate himself from his peers. Consequently, players perform in a similar fashion for most NBA coaches.
http://wagesofwins.com/2008/11/18/coaches-and-deck-chairs/Before we jump to the conclusion that most NBA coaches are just clerks with clipboards, we must acknowledge the inherent problems with measuring a coach's impact. First, coaching is collaborative, and accounting for the effects of trainers and assistant coaches (think of Tex "Triangle Offense" Winter and defensive guru Tom Thibodeau) is pretty much impossible. Second, at the risk of sounding like a motivational speaker, can leadership even be measured? Could you come up with a statistic to evaluate Doc Rivers' use of Ubuntu?It's also worth mentioning that not every basketball stats guy agrees with Berri. Dean Oliver, the director of quantitative analysis for the Denver Nuggets, examined NBA coaching in his 2004 book Basketball on Paper. Oliver's research was based on using various methods of establishing an expected number of wins, things like comparing a team's field goal percentage to its opponents'. Oliver then compared these expectations with a coach's actual record. His findings: Coaches like Phil Jackson can be worth up to an additional 12 wins per year. Oliver admits his methods have their limits, and even if a coach is exceeding expectations, it's hard to know exactly why. "I don't want to say seat of the pants, but many of the coaching decisions in the NBA are made so very quickly," Oliver says. "I'm not even sure that they could break down exactly what they were thinking at any given point in the game."
So, how do you know if your coach is doing anything worthwhile? To paraphrase Bill James, there's no consensus on what statistics should be on the back of a coach's trading card—in any sport. In basketball, where decisions are made on the fly, it's hard to break a game down into a set of discrete choices. Roland Beech, the statistical mastermind behind 82games.com, gave it his best shot, though. At the behest of ESPN columnist Bill Simmons, Beech created the Bad Coaching Index as a way to measure the efficacy of Doc Rivers' decisions. Beech compiled statistics on blown leads and offensive and defensive crunch time performance. The index, while mostly a goof, suggested that Rivers may not have been as bad as Simmons thought. Beech found that in 2004-05, Doc Rivers' Celtics came back to win 40 percent of the games in which they trailed in the fourth quarter, the fourth-best percentage in the NBA.
http://www.slate.com/articles/sports/sports_nut/2008/11/change_you_cant_believe_in.htmlMore reading:
http://freakonomics.com/2013/05/30/a-former-nba-coach-argues-that-coaches-are-not-responsible-for-outcomes/