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Measurability and Derek Jeter February 26, 2009

Skip Sauer at The Sports Economist had an interesting post about Houston Rockets forward Shane Battier’s lack of traditional stats and Rockets GM Daryl Morey’s belief in him regardless. Morey’s use of an adjusted plus-minus stat to justify hiring Battier is reminiscent of Billy Beane’s attention to on-base percentage in building the Oakland As as detailed in Moneyball.

What I take from Sauer’s post is that plus-minus is a surrogate variable for ability to be a team player. That opens the broader question of what can be measured and whether nonmeasurable statistics are ever useful in building a team.

If it’s not measurable, does it exist? Many people believe so. Think, for example, of clutch hitting, the vaunted (alleged) ability of certain players, such as Derek Jeter and David Ortiz, to hit more reliably in situations where the team’s expectation of winning or losing is weighted more heavily. The usual clutch situation is described as “close and late.” Clutch hitting is widely regarded by statistical analysts to be a myth, largely an artifact of small sample size. (In some cases, such as Jeter’s as identified in Wikipedia,the reputation for clutch hitting isn’t supported by any stats at all, but just a long memory for isolated incidences of close-and-late production.)

Jeter, predictably, thinks people who find statistical evidence that he doesn’t live up to his reputation should be defenestrated.

My opinion is that measurable and objective statistics are essential for valuing players (and coaching staff). The article on Battier is a red herring – Battier has what is presumably an anomalous plus-minus, particularly when accounting for distortions based on the quality of his teammates. Battier does, in fact, “have stats.” “Team player ability” isn’t a soft, undefined concept, but rather the ability to act as a multiplier for other players’ ability, and it’s measurable in final production numbers (probably as a factor of the player’s specific marginal product of labor). Battier’s plus-minus stat is evidence of an increased marginal product of labor.

Jeter, on the other hand, is a defensive liability who happens to be productive offensively. He’s a perfectly good hitter, but his numbers should be allowed to stand on their own rather than being propped up by some ephemeral idea that he occasionally produces at full ability and runs the rest of the season at some lower value of his optimal productivity.

High plus-minus is
evidence of production;
clutch hitting is not.