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Umpires are already more closely acquainted with pitch-tracking technology than is often assumed. “We currently use technology for both evaluation purposes and training purposes,” says MLB spokesman Mike Teevan. “All umpires receive a computerized breakdown of their plate performances, including calls they got right and calls they missed.”

The Zone Evaluation system, as the league’s PITCHf/x-based balls-and-strikes review heuristic has been dubbed, is one component of a comprehensive umpire assessment program. The league claims an average ZE umpire accuracy rate of 95 percent or higher, although certain pitches on which the umpire — but not PITCHf/x — is blocked by the catcher are excluded from the count. Even so, with an average of 156 called pitches per game (between both teams), a 95 percent success rate suggests that eight incorrect calls still slip through, too many not to notice. The explanation, contrary to what you may have heard from hecklers, isn’t that umpires are incompetent. It’s that their job is impossible for human beings to do perfectly.

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– http://www.grantland.com/story/_/id/9940495/ben-lindbergh-possibility-machines-replacing-umpires