Moser: Assessing the Cubs’ defense in a metric-less world

From SABR member Zack Moser at Baseball Prospectus on November 14, 2017:

If you have your ear to the ground, you might be hearing the beginnings of a seismic shift in baseball analytics. No—it’s not the mythical “bullpen revolution” that so many have seized upon as the privileged narrative of mainstream analytics writing. Truth be told, that “revolution” is merely the loudening machinations of the long march toward specialization, the narrative a product of a search for meaning in an era when baseball, The Game, feels its most meaningless. The rumblings that you hear are, rather, growing resistance to the stunted defensive metrics that grew out of the last era (or, possibly, two or three eras ago).

Can you feel it? It finds a voice in the pages of Baseball Prospectus, at the time overshadowed by the World Series. It’s whispered in hushed tones by player evaluators in our public analytics community. Questions about our evaluation of players’ defense are growing, and good baseball minds are picking apart assumptions upon which we’ve built defensive metrics and evaluation for a decade now. The truth is, we simply don’t know the usefulness of the metrics we currently enjoy, and it’s increasingly frustrating to both watch analysts tout defensive metrics as gospel, and to come up short every time in describing a player’s defensive ability. How can we pin a number, a run value, to a player’s defensive performance if we don’t even know the degree to which positions are differentiated or how different skill sets translate to positional changes, if we don’t have enough data involving position players of varying skills switching positions?

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Originally published: November 15, 2017. Last Updated: November 15, 2017.