One aspect of new-breed basketball metrics is that many people have different ways to add up the quality of the players on the floor, which can then give you a way to guess at which team might win.

But ... what's missing from those equations?

Coaches.

Do coaches matter?

My knee jerk reaction is: Of course they do.

The best way to prove that would be to have coaching staffs swap rosters again and again in some kind of grand long-term experiment. If I'm right, you could give every NBA coach essentially the same players over time, but some would win significantly more than others.

But that experiment is imperfect (it ignores long-term development, for instance -- Coach A might get you practicing your free throws, and you might show results when you're playing for Coach B) and more importantly, will never happen.

So we're left with small sample sizes, and fancy guesswork, none of which seems to prove that your coach makes all that much difference.

On Slate.com, Ryan McCarthy investigates:

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).

McCarthy acknowledges that there are plenty of dissenters, including Dean Oliver, who think coaches have more value.

But think about it. What a miserable article to read if you're a coach. All those late nights of film study. All that competition for your job. All those tricks learned at conferences. All those books by the masters you have internalized.

And now there is evidence to support the notion you could be replaced by a deck chair.