I just read an article about the difficulty of determining the value of an NBA coach. Careful statistical analysis and recording of lots of data still makes it nearly impossible to gauge the effect of a coach.
Basketball as a sport is the least-quantifiable of the major sports. Baseball is the most easily quantifiable. It is made of of discreet steps and one-on-one confrontations between pitcher and batter.
But perhaps the problem isn't with the data, it is with people. We have a love for numbers, for quantifiable effects, for a head-to-head comparison between rivals to determine the worth of each component. But is this a cognitive bias?
A successful team is a synergy of 12 players, each with a different role, different skills, different physical attributes, and different number of minutes played. Also, only five players can play at a time, so mixing and matching of skills and suitability occurs. The coaches are required to find the right mix of players, playing time, and also fit it in to the context of the flow of the game. Lastly, their is the opponents team to consider, and how well the players on the floor work together to beat the opposing five players, who are also struggling to find their own right mix.
As one can tell, it gets messy fast. Things like personnel skills and human resources though are not quantifiable. It seems that a love of science and numbers frequently blinds people to the two different sides of our brain. One is mathematically inclined, the other is artistically inclined. A problem can have both a numbers side (shooting percentage, number of rebounds) and an artistic side (are these players working together well).
Jeff Van Gundy always struck me as a coach who had a strong affinity for the numbers and technical aspects but never had a clue as to the inter-personal, synergistic side of basketball. Phil Jackson strikes me as more of a coach who is best when he has really good players and figures out how to get them to work together and utilize their talents. I don't think his value is in reminding Kobe to block out or the proper technique. Its in provoking Kobe to want to block out. Jeff knows more about blocking out, but Jackson can get him to do it.
NBA players are a finished product by the time the arrive on the scene. You can't change a man's heart but you can certainly squash out the flame inside him.
Anyways, I think that judging the effect of a coach is more of a right-brain activity which can only be judged and discussed, but trying to quantify it is a laughable activity.
I also think that successful investors in sports are the only people truly qualified to give a valuable opinion on more qualitative judgements. They are paid to be right and punished if they are wrong.