New York Yankees manager Aaron Boone reacts to umpire Chris...

New York Yankees manager Aaron Boone reacts to umpire Chris Guccione after being ejected during the third inning against the Baltimore Orioles in an MLB baseball game at Yankee Stadium on Thursday, May 25, 2023. Credit: Kathleen Malone-Van Dyke

You would think after seeing a highly agitated Aaron Boone go ballistic on plate umpire Edwin Moscoso on Thursday night that the Yankees’ manager couldn’t wait to welcome the robots.

And why not?

Baseball is armed with so much bleeding-edge tech in the 21st century that everyone knows in a blink whether the ump blew a call or not. Boone ran from the dugout flashing four fingers, evidently a reference to the four strikes Moscoso missed — information that’s easily confirmed by any fan with an iPhone.

By the next morning, the popular website proved Boone’s suspicions correct, detailing that Moscoso had whiffed on eight strikes, calling them balls instead. Boone was especially furious that Moscoso’s amoeba-like zone led to Yankees starter Clarke Schmidt having to throw 29 pitches in the first inning alone, which would shorten that night’s outing. But the manager wasn’t stumping for robot reform just yet.

“I’m not advocating for the robo umps,” Boone said afterward. “I think these guys do — for the most part — a great job and work really hard at it.”

Duly noted.

But the robots already have reached MLB’s doorstep anyway, with the automated ball-strike system (ABS) now being used at all 30 Triple-A stadiums this season. It’s only a matter of time before the mechanized takeover advances to baseball’s highest level, but two questions remain: the arrival date and format.

Both will become clearer in the months ahead. Given the unbridled success of this year’s trio of rule changes, particularly the literal game-changing impact of the pitch clock, commissioner Rob Manfred could feel emboldened to implement some version of the ABS for the 2024 season.

While Manfred has the power to do so under the collective bargaining agreement, through the consultation of the Joint Competition Committee, sources indicate that MLB’s power brokers are proceeding cautiously to make sure the system is as close to airtight as possible before an MLB rollout.

As for the format, Triple-A teams are experimenting with two ways to utilize the ABS. For the first three games of each six-game series, the Hawk-Eye technology (the same that monitors the lines at Wimbledon or the U.S. Open) is relied on exclusively to call balls and strikes, with the plate umpire getting word via an earpiece.

For the last three games, it switches to a challenge option — the umpires will make the calls as they traditionally do, but teams have the ability to overturn them, based on verification by the ABS. Each team starts with three challenges, and correct ones are retained.

Between the two, the challenge format appears to be the preferred option and is gaining momentum down in the minors, for a few reasons. By allowing the umpires to still govern the strike zone, it’s less radical and preserves that human element of the game. Also, the challenge feature has the capability to fix clear misses, which is the primary focus of any review function.

Through May 21, strike/ball calls were overturned at a 43.8% rate in the International League and 44.4% in the Pacific Coast League, with an average of five to six calls challenged each game.

An additional bonus: there is the entertainment value of challenging calls, with people able to see the playback on the scoreboard.

“It is exciting,” said the Yankees’ Ryan Weber, who recently was pitching for Triple-A Scranton. “For the two teams, the fans. Because they put it on the screen.”

Maybe just not as fun for Weber, who went 0-for-2 in his two challenges (only the pitcher, catcher and hitter are allowed to make a challenge, and immediately following the pitch). But that was the puzzling part for Weber, because he was convinced those two pitches were in the strike zone. And yet when they showed up on the screen, one of them “looked completely different,” Weber said. That was a head-scratcher, and it made him wonder if the ABS system still has significant bugs to correct.

“You almost feel like you have to throw the ball down the middle,” said Weber, a high-80s thrower who relies on finesse rather than velocity. “Especially like my style of pitching where I try to throw to the corners. I like to get that call that’s a tick off the plate, and you’re just not getting it anymore.”


Tinkering with it for years

With a computerized tracking system, there’s no more nuance, no variance between umpires. Just a precise boundary. In theory, that should be a good thing — eliminating human error. No more blown calls, right? But according to Weber, that can be problematic in itself if you can’t determine exactly where those lines are drawn, which was the case for him.

“I would ask after the game, the pitching coach or the manager, hey, can I see a printout of the strike zone of what was called a ball and what was called a strike,” Weber said. “We’ve never been able to get it. For us not to get eyes on it, I found it’s not fair.”

Pitchers mostly know what they’re getting with human umpires. Some are prone to low strikes, for instance. But if MLB’s decision-makers are dialing in a strike zone to their own modified specifications and it veers away from the more traditional interpretation, then providing some transparency with that new blueprint would be helpful, as Weber suggested.

Tinkering with the strike zone is not an unprecedented phenomenon. It’s gone through myriad transformations through the years, in response to the sport’s trends, before settling on the current dimensions. Since 1996, the uppermost border is the midpoint between a batter’s shoulders and the top of his uniform pants while the bottom is just below the kneecap. At least that’s what the rulebook dictates. Umpires tend to have their personalized interpretations.

But MLB’s development of the robo umps is not only about maintaining a more accurate strike zone. In recent years, Manfred & Co. have been determined to create an uptick in on-field action — more contact, more offense, fewer strikeouts — and one of the better methods toward achieving those goals is to tailor the zone accordingly by tilting it to favor hitters.

A similar thing was done after the 1968 season, otherwise known as “The Year of the Pitcher,” when the ceiling of the strike zone moved from the shoulders down to the armpits and the bottom rose slightly to the top of the knees (the mound also was lowered from 15 inches to 10). More than a half-century later, hitter-friendly changes are still being made to the modern game, with this year’s shift ban and also the pitch timer (to some degree) becoming new allies to the offense.

It’s not as if MLB is hiding those intentions, either. The ABS system was first deployed under limited use at Triple-A last season, but for this year, the strike zone was narrowed from 19 inches to 17, the latter being the true width of the plate. With MLB now using the minor leagues as a laboratory for whatever rules-related ideas spring to mind, the game can be tweaked any number of ways to achieve the desired effects, and that seems especially true with the development of the ABS system.

Targeting strikeouts is the constant focus, as the K is Public Enemy No. 1 to baseball’s main objective: more balls in play and thus greater entertainment value for the sport. But hitting is hard, and pitchers throw with more velocity and movement than ever, so MLB’s strikeout percentage — currently at 22.7% — has stubbornly remained in that range the past few seasons (but down from 24.1% in 2021).

To date, those numbers are similar to what’s happening at Triple-A, even with the ABS. The International League has a 22.6% strikeout rate with the full ABS, 22.0% using the challenge system. For the Pacific Coast League, it’s 22.0 and 21.4, respectively.

MLB’s studies have shown that a shorter, wide strike zone encourages more contact, so it’s probably correct to assume that’s how the ABS will be calibrated whenever the robo umps do arrive, certainly sooner rather than later.

“I feel like it’s close,” Weber said. “At Triple-A, they’re using it 100% of the time, not just one or two games a series. It’s every game, so it’s got to be close to coming here.”

And when it does, maybe Boone’s ejection rate will go down, along with his suspensions.

Even if the umpires maintain some authority, the robots ultimately will have the last word.

The Robo-Ump Effect

With the automated ball-strike (ABS) system currently in use at all 30 Triple-A ballparks, here’s some of the data, broken down by league and either the “full” ABS — the game called exclusively by the tracking system -- or the challenge format, which only uses it for verification. For comparison, MLB results through Friday’s games also included.

International League

Full .................. 2:38 .... 10.7 R/G ... .258 BA ... 22.6 K% ..... 12.5 BB%

Challenge ....... 2:41 ..... 11.0 ........... .267 ........ 22.0 K% ...... 11.5 BB%

Pacific Coast League

Full ...... 2:44 ....... 12.4 R/G .... .268 .........22.0 K% ...... 13.5 BB%

Challenge ... 2:46 ....... 12.0 ......... .277 ......... 21.4 K% ........ 11.9 BB%

MLB ......... 2:37 ........... 9.1 R/G .... .247 ...... 22.7 K% ....... 8.8 BB%


International League

Offense .............. 2.41 per game ..... 48.2% overturn rate

Defense ............. 2.76 ...................... 39.9%

Total ................... 5.17 ....................... 43.8%

Pacific Coast League

Offense ............. 2.67 per game ......... 41.2% overturn rate

Defense ............ 3.15 .......................... 47.1%

Total ................... 5.82 ......................... 44.4%

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