For almost one-quarter of the NBA's 30 teams, 2008 is a year of change. Whether it's Mike D'Antoni's fast-paced offense in New York or Larry Brown getting the lowly Charlotte Bobcats to "play the right way," fans in seven cities have new head coaches and great expectations. They shouldn't get their hopes up. Despite years of careful analysis, nobody has determined what it is that NBA coaches actually do.
In all sports, the coach's supposed mission is to impart wisdom to his callow charges. In the NBA, though, the students sometimes have just as much coaching experience as the teacher. Along with vets like D'Antoni and Brown, this year's new class includes Vinny Del Negro of the Bulls, who has never coached anyone on any level. Michael Curry, who replaced veteran NBA coach Flip Saunders in Detroit, has served just one year as an assistant. In a couple of years, both could very well be out of work. A back-of-the-envelope calculation shows that the average tenure of today's NBA coaches—the amount of time each coach has spent in his current job—is just more than three years, about a year shorter than the current figure for the NFL and MLB. (The figure is even smaller if you account for Jerry Sloan's tenure in Utah, which dates back to the Reagan administration.)
Del Negro and Curry are, of course, ex-NBA players—a reliable back door into the NBA coaching cabal. Hiring a contemporary pro, we're told, is a smart move—nobody can relate to today's player like a recently retired jock. But despite this hiring strategy, the NBA is the only league in which coaches regularly get "tuned out"—that being the condition in which players stop paying attention to everything that comes out of their boss's mouth. Just two years ago, Avery Johnson led the Dallas Mavericks to the NBA Finals. This summer, Mavs owner Mark Cuban reported that Johnson had alienated his players to the extent that they demanded trades unless he was fired. The players weren't traded. Instead, the Mavericks dumped Johnson and replaced him with Rick Carlisle, who had previously been tuned out by the Indiana Pacers.
If you think that being an NBA coach sounds a lot like having a position in human resources, you might be right. According to a new study co-authored by 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).
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.
In the NFL and MLB, stat geeks and economists have made more serious attempts to measure the impact of similar situational decisions—that crucial call to the bullpen, the choice to go for it on fourth down. But even in the coach-as-deity world of the NFL, a place in which a writer can earnestly pen a tome called The Genius: How Bill Walsh Reinvented Football and Created an NFL Dynasty, there's still no magic data on coaching effectiveness. The same goes for baseball. In his 1997 book The Bill James Guide to Baseball Managers, the baseball writer came up with a makeshift ranking of the greatest field generals of all time but also insisted that there's no such thing as a good or bad manager. Instead, he argued, managers are specialists: Tony La Russa likes the hit-and-run, Bobby Cox loves to platoon, and Sparky Anderson is the king of the intentional walk.
Berri's study shouldn't be interpreted to mean that NBA coaches don't have strengths and weaknesses. Mike D'Antoni and Don Nelson are known as offensive gurus; former Rockets coach Jeff Van Gundy, who tutored Celtics assistant Tom Thibodeau, is more defensive-minded. It's also probably not fair to assume that Berri's work supports the classic complaint that the NBA is dominated by the whims of self-serving millionaire athletes. NBA coaches seem to have their biggest impact when their tendencies blend with their players' quirks. (The New York Knicks' castoff group of shoot-first players seems to be doing fine in D'Antoni's run-and-gun offense.)