The Observer Effect
Half a season into MLB's robot-umpire era, the machine's biggest effect on baseball has come from the calls it never made. Umpires shade toward the machine's zone, hitters have learned to wait, walks hit a rate unseen since 1950 — and knowing the strike zone better than the umpire is now a measurable, tradable skill.
Twenty-one and four.
That was Carson Kelly’s record on challenged ball-strike calls as the Cubs’ catcher when ESPN checked in this May — twenty-one calls overturned, four lost. Baseball Savant scored the work at 2.3 runs above expectation. Not runs from hitting. Not runs from framing, blocking, or throwing out runners. Runs from knowing the strike zone better than the umpire standing behind him, and proving it, in public, twenty-one times out of twenty-five.
A year ago that skill did not exist as a measurable thing. There was no column for it, no run value, no leaderboard. Now there is a public dashboard.