For the first time, sensors and a computer play umpire in a pro baseball game

SAN RAFAEL, Calif.—It turns out 21st century baseball with a computer calling balls and strikes feels a lot like 20th century baseball (you know, with a human behind the plate). There appear to be two main differences. The first and most obvious is volume. Machines just aren’t good at giving that classic umpire grunt, so you still need a warm body to do it.

The second? Accuracy.

"You face [Hall of Fame pitcher] Greg Maddux and he’d get a foot off the plate," recalls Eric Byrnes, former Oakland A's player and current baseball analyst. "So if we have a chance to get it right, if we have a chance to get a pitch every time, why would we not?"

Byrnes was the man behind Tuesday night's historic technological feat. On a picturesque evening in Marin County just north of San Francisco, the San Rafael Pacifics faced off against the Vallejo Admirals in what was billed as the first professional baseball game to be called by a piece of technology rather than a person. In this minor league showdown, the role of the balls-and-strikes umpire was played by a mounted three-camera tracking setup synced with a computer. (Two of the cameras are mounted at each end of the upper corner of the grandstands behind the plate; the third sits in center field.) Together, the devices comprise a system better known by its commercial moniker: Pitchf/x. It was soon dubbed #RoboUmp on Twitter.

"I’m not looking to eliminate any umpires, not one. If anything, we’re essentially going to add an umpire," Byrnes noted. Accordingly, there were still two standard umpires on the field and another behind the plate. That's the standard setup of the Pacific Association of Professional Baseball Clubs, an independent league in the San Francisco Bay Area (it's considered a Single A equivalent). But rather than his usual duties, the homeplate umpire largely remained silent, only calling foul balls and any potential plays at the plate.

Byrnes, for his part, gave the technology a voice. Mic'd up during the game, he'd grunt "STRIIIIKE" with an umpire's gusto and flatly call "ball" with every outside pitch. And unlike a traditional umpire, Byrnes could occasionally let some personality in. "Just caught the outside corner dude, and I'm talking just nicked it."

Vallejo Admirals third baseman Joshua Wong told Ars before the game that he was encouraged by the Pitchf/x tests he saw.

"I feel like it speeds the game up more, it gets the hitters to swing at more pitches," he said. "It’s good for the game. Just being more accurate and having better calls is going to help us more."

Old tech, new experiment

Pitchf/x isn't a new invention. It has been in use behind the scenes for a decade to record both the precise location and trajectory of pitches. It’s already used in all 30 Major League Baseball parks for analytics purposes as well as online and television broadcasts. If you've seen a Sunday Night Baseball game on ESPN, you're familiar with Pitchf/x's work. (A predecessor system by a now-defunct company, whose product was called PitchTrax, debuted as far back as 2002.)

In many ways, Major League Baseball has historically been averse to adding technology. Unlike other sports that have at least embraced computers or cameras for scoring confirmation or play reviews, MLB instant replay only debuted in full during the 2014 season. But when it comes to utilizing a RoboUmp for something as integral to the game as pitcher-hitter interactions, technology must cope with uncertainty. Consider MLB's inherently relative definition of the strike zone:

The STRIKE ZONE is that area over home plate the upper limit of which is a horizontal line at the midpoint between the top of the shoulders and the top of the uniform pants, and the lower level is a line at the hollow beneath the kneecap. The Strike Zone shall be determined from the batter's stance as the batter is prepared to swing at a pitched ball.

In other words, it’s roughly the space over the plate measured from the armpits or letters across a player’s chest to the knees. It literally changes from hitter to hitter. And as any good pitcher knows, it may slightly change with every umpire. Identifying where that space is in a split second, particularly in the lower or higher corners, is more art than science. Catchers also play a role by attempting to frame a pitch by quickly adjusting their gloves after the catch to indicate to the umpire that the ball was, in fact, caught in the zone.

Umpires do their best, but they make mistakes. Heckling and coaches' arguments wouldn’t be part of the game if they were perfect every time. For its part, Pitchf/x’s hardware defines a strike as any ball that touches the strike zone—which likely means that some players won’t like what they saw thrown to them.

"I'm sure many people around baseball will be watching the debut of this new system to see how it goes," Jacob Pomrenke, a producer at the Society for American Baseball Research, e-mailed Ars. "There will always be some kinks to work out and it will be intriguing to see how the players respond (especially to calls they don't like!). The idea of using an automated system to call balls and strikes has been talked about for years. It'll be nice to finally have a real-life example to see how it works at the professional level, but there are still a lot of factors that would have to go into the decision to implement this type of system at the major-league or the affiliated minor-league level. This is a system that is very dependent on precise technology, and even the Pitchf/x system that MLB has used for nearly a decade now continues to have hiccups and glitches that require human intervention."

Pomrenke pointed out that most problems the software has had were relatively minor. Grantland outlined a few such errors from this exact setup in 2013, and most had to do with mis-calibration. In order for sensors and software to replace human umps, fans and the MLB would have to be "willing to accept a much smaller amount of inexplicable error in exchange for a larger amount of explicable error," Dan Brooks, founder of Pitchf/x repository and BrooksBaseball.net, told Grantland at the time.

This is a mis-drawn strike zone, as seen in 2013. Credit: Grantland

The implementation of RoboUmp on this night is essentially a passion project for Byrnes. If all goes well (the "ump" will work tomorrow's game, too). He hopes that future home plate umpires could work in tandem with a Pitchf/x-like system, utilizing something resembling a watch that was in use for the 2014 World Cup to alert refs about goal-line technology.

"I think when you do see this in the major leagues, it will be very clean, it’ll be something where the fans won’t even notice," he added.

As for things in Marin County, this was one time where the umpire truly did steal the show. The game itself moved along briskly but largely without action; San Rafael led 1-0 in the sixth, and the two teams combined had fewer than 10 hits total. Chatter in the stands instead focused on the ump, most of it supportive. No one showered the tech with familiar boos or "You suck, ump!" refrains.

For those involved with the experiment, like Pacifics’ Assistant General Manager Vinnie Longo, they hope such talk is a sign of things to come.

"If the system does well, we're going to have a great storyline to talk about for the next couple of years," he told Ars.

Listing image: Cyrus Farivar

Cyrus Farivar Editor at Large

Cyrus is a former Senior Tech Policy Reporter at Ars Technica, and is also a radio producer and author. His latest book, Habeas Data, about the legal cases over the last 50 years that have had an outsized impact on surveillance and privacy law in America, is out now from Melville House. He is based in Oakland, California.

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