Gerry Davis was speaking to a crowd of baseball fans at the Society for American Baseball Research’s annual convention in San Diego last Saturday when he let something slip.

Davis was describing a tough day at work. The night before, he was the home plate umpire in a game between the Padres and Cardinals. Vic Carapazza was the first base umpire. The Padres challenged two of Carapazza’s calls: a safe/out call on a grounder in the second inning, and a pickoff attempt in the third. Both calls were overturned. Later, the Cardinals challenged two more of Carapazza’s calls. Both were overturned.

Davis was the crew chief, so he wore the headset while each call was reviewed in MLB’s remote video room. Four times, Davis was the first to hear each verdict delivered. Four times, he confirmed what the announced crowd of 33,329 might have suspected: an umpire was wrong.

“If that had been me (umpiring first base), you’d be walking me off the ledge,” Davis told the crowd. “That, or hide the razor blades kind of thing.”

The big reveal wasn’t that Davis, the man with the most consecutive seasons as a major league umpire (38), has the darkest sense of humor in the game. That came a minute later:

“The vast, vast majority of our ejections nowadays are over balls and strikes,” Davis said. “The reason is, there’s no replay for that. I don’t want to say never because 15 years ago I wouldn’t have been sure there would be replay now. So I can’t say there will never be (replay for) balls and strikes, but the technology’s not there right now. They were going to do it in Atlantic City and the system wasn’t capable of doing it.”

Did you catch that? Maybe not. Davis misspoke. He meant the Atlantic League – the independent minor league that planned to test a radar-assisted strike zone in 2019. The TrackMan devices in each park would be calibrated to determine whether or not a pitch passed through a defined strike zone. In theory, Atlantic League umpires would take their cue from TrackMan before making their call.

In practice?

“The box that you see on TV – which by the way is the same size for Aaron Judge as it is for Jose Altuve – it’s also one-dimensional,” Davis said Saturday. “And I know for a fact there are pitchers that have good enough control that they could throw a ball where it would bounce the ball on the plate and it would cross the strike zone and the hitters would go much more berserk than they do nowadays. I don’t want to say it’ll never occur, but it’s just not capable yet of doing it because the strike zone’s three-dimensional.”

Davis was half right. The Atlantic League hasn’t been able to implement the TrackMan strike zone – but not because the strike zone is three-dimensional.

“We did not know how we would be communicating to and from umpires,” said Rick White, the Atlantic League’s president. “There was a lot to work out. The original devices we had were radio wave-based, so we needed an FCC channel, a walkie-talkie device. … We needed earpieces once we decided umpires would still be signaling balls and strikes. Then we moved from there to a secure WiFi signal across the field that could not be hacked by casual observers. We’re in that zone.”

White said the league never formally announced a debut for this technology, and published reports described its scheduled roll-out in vague terms. TrackMan wasn’t even up and running in every Atlantic League park when the season began in April, White said. Now there’s a formal date for baseball’s first radar-assisted strike zone: July 10 in York, Pennsylvania, at the league’s annual All-Star Game.

“As the ball crosses the plate within the vertical cube, or the sphere of the individual players’ strike zone, the TrackMan system determines whether it’s a ball or strike,” White said. “All players have their own individual strike zone. The system then declares ‘ball’ or ‘strike.’ The signal is then being transmitted to the umpire.”

How? The home plate umpire’s earpiece will produce a pre-recorded man’s voice that says “ball” or “strike” after each pitch. (White insisted the voice is not his, a selfless abdication of power.) Ironing out even small details like cadence – how soon after the ball crosses home plate should an umpire hear the vocal prompt? – became a time-consuming process of trial and error. By the time the Atlantic League was satisfied with its process, the technology was already in place. The TrackMan strike zone was ready.

This is a breakthrough in itself. As Davis pointed out, the most popular strike zone maps (on television, on MLB’s mobile app, etc.) are two-dimensional and unaffected by the variance in batter height. That can have practical consequences of perception.

When Mark T. Williams, a Boston University researcher, determined there were an average of 14 incorrect ball/strike calls per game in 2018, he culled his data from Statcast. Yet even this technology, which is owned by MLB itself, produces data bound by the same limits as the other strike-zone detection tools. A pitch thrown to Judge (listed as 6-foot-7) and Altuve (5-foot-6) elicits the same data point on a two-dimensional grid.

Speaking Saturday, Davis said the error rate on ball/strike calls league-wide is 3 percent. Yet according to Williams’ research, even the best umpire (John Libka) missed 7.59 percent of his calls. The most puzzling aspect of this discrepancy: Williams used MLB’s front-facing, proprietary data to arrive at his error rate. Why should Davis, an umpire employed by MLB, have a different number at his disposal?

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Julio Urias strong in bulk but Dodgers lose to A’s in ninth Perhaps the answer resides in the limits of the Statcast strike zone, though it’s puzzling that the league’s front-facing data would fuel the perception that its umpires are less able than they actually are. Even if the error rate on balls and strikes is only 3 percent, as Davis claims, there’s another obstacle standing in the way of a radar-assisted strike zone coming to MLB: Its umpires belong to a union, the MLB Umpires’ Association, which has consistently pushed back against calls for a strike zone defined by technology. Atlantic League umpires aren’t unionized.

“Our umpires have been nothing if not supportive,” White said of the TrackMan strike zone. “The players to a man are supportive of it because they’re finally going to play by a rule-defined strike zone that is consistent throughout the league.”

Even if there are no technological mishaps along the way, TrackMan still bears the burden of proof that it can enforce the fairest strike zone. Will any pitchers throw curveballs through the strike zone that land on home plate? If so, will they all be called strikes? Either way, how will batters and pitchers react and respond?

The human element might be unavoidable, even in the electronic age of balls and strikes. Hide the razor blades, indeed.