Over at the Wages of Wins Journal (one of my favorite NBA blogs), there is a raging debate on the value of coaches. The general premise of Arturo Galletti’s post is that coaches in the NBA only matter in one regard: allocating playing time. Every other facet, like when you hear that a coach is making the team “tougher”, or is a “players coach”, doesn’t mean a thing. Their only value is determining which players see the floor, and which ride the pine.
I also believe that coaches add very little value to a team. Time after time it is shown that best way to predict how a team will perform is to look at the past statistics of the players: they are a much better indicator of a team’s strength then anything having to do with the coach. I want to take Arturo’s point a little bit farther though. In arguing that a coach’s main impact is allocating minutes, he implies that the allocation of minutes is an important consideration in whether a team wins or not. I know this sounds ludicrous, but I am suggesting that allocating minutes properly to the best players on the team, while important, doesn’t matter too much.
The above chart is simply a graph of two columns of data found in Arturo’s post: the percentage of minutes coaches properly allocated, and the total of a team’s wins produced. You would think that there would be a high correlation between these two numbers: teams that gave minutes to their best players would tend to do better than teams that did not. As it turns out, this correlation isn’t too strong, with an r2 of only 0.39. This means that, roughly speaking, 39% of the total of a team’s wins produced is due to the proper allocation of minutes. That is strong evidence to suggest that minute allocation matters, but equally strong evidence that it doesn’t matter too much. Even if Toronto Raptors coach Jay Triano had allocated his players minutes efficiently last year (instead, he only allocated 3% of his player’s minutes properly, no wonder he got fired), they would still have sucked. The fact is, better minute allocation can’t make up for bad players.