Generally speaking, a decent proxy for a batter’s understanding of the strike zone is his O-Swing% — that is, the percentage of pitches outside of the zone at which he offers. The lower that figure, the less often a player is offering at pitches outside of the zone. The less often a player is offering at pitches outside of the zone, the more likely he is both to draw walks and (one assumes) swing at better pitches inside the zone.
As to the first point, that is borne out by the numbers: O-Swing% and walk rate correlate rather tightly. Consider the following graph, for example, which includes the O-Swing%s (from the PITCHf/x zone) and walk rates for all 143 qualified batters from 2012. (Note: average O-Swing% among this population is 28.9%. Standard deviation is 5.7%.)
As for the second point, however — that O-Swing% necessarily indicates a better idea of the strike zone — it recently occurred to the author (who isn’t very sharp) that perhaps these are not the same thing. Anyone who ever saw Mark Bellhorn bat, for example, will know that it’s sometimes possible for a player not only to refrain from swinging outside of the zone, but also to avoid swinging altogether. There is a difference, however, between selectivity — which we’ll define, for the sake of this post, as “ability to discern between balls and strikes” — and a refusal to swing the bat. The former, we reason, is a good thing; the latter, less so.
Read the rest of this entry »
