All Podcasts / 99% Invisible / RoboUmp Hits the Big Leagues
99% Invisible
99% Invisible

RoboUmp Hits the Big Leagues

April 14, 2026 • 31m

Summary

⏱️ 8 min read

Overview

This 99% Invisible episode explores the introduction of robot umpires (ABS system) in baseball, examining the trade-offs between accuracy and human elements of the game. Originally broadcast in 2023 and updated for 2025, the story follows the journey of automated ball-strike calling from minor leagues to Major League Baseball, revealing unexpected consequences for both the sport's drama and the umpires themselves.

The 1997 Umpiring Disaster That Changed Everything

The episode opens with the infamous 1997 playoff game where umpire Eric Gregg made egregiously bad strike calls for pitcher LeVon Hernandez, who struck out 15 batters despite consistently missing the strike zone by feet. This game exemplified the human error problem in baseball, with umpires blowing approximately 14 calls per game, totaling 34,000 bad calls annually. The incident helped spark the decades-long conversation about whether technology could improve the game's accuracy.

  • LeVon Hernandez struck out 15 batters in Game 5 of the 1997 NLCS, but many weren't actually strikes
  • Umpire Eric Gregg called pitches as strikes that were "a foot, two feet outside of the strike zone"
  • Studies show umpires blow about 14 calls every game, totaling 34,000 bad calls per year
  • Human umpires get it right about 94-97% of the time on strike calls
" This pitch is, I would say, a foot, two feet outside of the strike zone. Not close, called a strike. "
" It was probably the worst umpiring I can remember. The outside of this strike zone, it just didn't end. It was like a never-ending strike zone. "

How Robot Umpires Actually Work

Modern robot umpires aren't actually robots but sophisticated HD camera tracking systems based on missile tracking technology. The ABS (Automatic Balls and Strikes) system uses cameras already installed in stadiums for TV broadcasts to track every pitch with extreme precision. A human umpire still stands behind the plate and receives the call through an earpiece, then announces it to the crowd, creating a collaboration between technology and tradition.

  • The system uses HD cameras and missile tracking technology to determine balls and strikes
  • Most MLB stadiums already have sophisticated ball tracking systems for TV broadcasts
  • The system tracks exit velocity, spin rate, and every revolution of the baseball
  • Human umpires still announce calls after receiving them through an earpiece - the voice says 'ball' or 'strike'
  • Fred DeJesus was the first umpire to use ABS in 2019, and his earpiece is now in the Baseball Hall of Fame
" They have these very sophisticated missile tracking systems, essentially, in ballparks. "
" The strike is very peppy and, you know, sounds very encouraging and the ball is ball, kind of disappointed. "

📚 5 more sections below

Sign up to unlock the complete summary with all insights, key points, and quotes

Listen on Apple Podcasts More Episodes from 99% Invisible