During the summer, San Rafael's Albert Park baseball stadium typically draws around 450 people to watch the minor-league San Rafael Pacifics. On this Tuesday evening, though, there are close to 900 for an independent Pacific Association game against the Vallejo Admirals. There's a handful of local broadcast news crews as well—but their cameras aren't trained on the field. Instead, all eyes are on a small monitor at the right edge of the backstop, where Eric Byrnes is watching the game on television.

The Pacifics' Wander Beras throws the game's first pitch. It seems a little high, but the home plate umpire, a 40-year veteran named Dean Poteet, doesn't react at all. Instead, back by the backstop, it's Byrne, a former major league outfielder, who leans toward a microphone and lets out a loud "HYAHHHH!" that resounds through Albert Park. The first pitch in the first professional baseball game to be called by a computer instead a human umpire is a called strike.

Since retiring from the majors in 2010, Eric Byrnes has held various radio and television commentating gigs. But after playing some games with the San Rafael Pacifics last year, he came back to them with an idea to use PITCHf/x. The three-camera tracking system, designed by Sportvision, already collects pitch location, speed, and movement data in major league parks, but Byrnes wanted to use it to actually determine the game's balls and strikes. Since the Pacific Association is an independent league, it's outside of Major League Baseball's purview, and so could move much faster than the organization's traditional glacial pace.

ESPN's Pablo Torre makes frequent references to the impending "robot umpire revolution," the idea that computer technology will become so accurate at detecting locations for sports plays that fallible humans will become obsolete. And sport purists like Keith Olbermann deride the injection of technology into the game.

Still, over the past three decades, a deluge of sabermetric data has made baseball analysis almost atomically granular. The use of video tracking technology to capture a large set of player data has ballooned significantly in the past decade, and it has translated into beautiful data visualizations that convey complex information to viewers in easily digestible fashion. But that statistical analysis hasn't yet been applied to the way the game is adjudicated. That irrevocably changed Tuesday night.

PITCHf/x is only one of the visualization systems created by Sportvision. The Fremont, California-based company pioneered the yellow 1st-And-10 Line seen on football broadcasts, as well as NASCAR race tracking and the LiveLine system used during broadcasts of the 2013 America's Cup.

The system is impressive for its simplicity. PITCHf/x uses three cameras to triangulate a baseball's position in space from the moment it leaves the pitcher's hand. But there's one major flaw: the cameras stops tracking the ball a few feet from the plate, instead analyzing the trajectory to come up with a predicted location within an inch of where it actually shows up. Vince Gennaro, the president of the Society for American Baseball Research (SABR), is quick to point out that that's immaterial, since data collection is the system's sole purpose. "It wasn't set up to in fact call balls and strikes," he says.

Former major league outfielder Eric Byrnes uses a computerized video system to call balls and strikes at an independent minor league baseball game between the San Rafael Pacifics and Vallejo Admirals Tuesday, July 28, 2015, in San Rafael, Calif. On Tuesday night, the computer system stood in for pitch calls in what is considered to be the first professional game without the umpire making those decisions. A full umpiring crew will be there for everything else. (AP Photo/Eric Risberg) Eric Risberg/AP

Yet, that blind spot in front of the plate troubles the sabermetric community. "One inch is an enormously wide error band around which to call balls and strikes," Gennaro says. Bill Savage, another SABR member, echoes the fears of millions of baseball purists. "It would be great," says Savage,"if we could trust the technological guidelines to be accurate"—but as things are, he would "prefer the failure rate of human beings to the potential failure rate of machines."

For their part, Sportvision wants absolutely nothing to do with the conversation about increasing the use of technology in baseball. None of the company representatives surrounding the Sportvision truck down the third base line agree to be quoted, but they're happy to talk casually about the history of PITCHf/x and explain it to fans. At one point, though, a line drive is hit into right field, and an umpire rules it fair. It's a questionable call; "not our system!" says one the Sportvision representatives.

For the company, PITCHf/x is a pure observational tool, providing raw pitch data that can be used by teams to analyze players and by broadcast partners to provide fans and viewers with a better idea of where the ball lands relative to a general picture of the strike zone. It's the same guiding principle behind the yellow line in football and the onscreen graphics during motorsports events: give viewers more data and better visuals to make tracking sporting events easier.

And the system already has wider applications: Since being installed in all 30 major league parks, it has been used to audit umpire performance. Many teams have even paid to install the system in their minor league affiliates' stadiums, in order to keep tabs on players' development.

In the early innings, Byrnes yells like a madman to call strikes and even lightly taunts pitchers and batters, letting them know how close or far away a pitch was from the strike zone. It's a strange thing to hear live commentary over a PA system during the game; it lends Byrnes an air of ringmaster. But it's even stranger to look at the home plate umpire, with few baserunners and no runs scoring, mostly standing with arms at his sides, focused on the pitcher and the plate. (After the game, he mentions to reporters that it was difficult to keep from motioning for strikes, but that taking the decision-making out of his hands freed him up to better call check-swing strikes.)

But after an uneventful hour or two, there's finally a meaningful moment in the bottom of the sixth inning. The Pacifics are up, and with two men on base, a pitch comes in; Tim Fitzgerald, the visiting broadcaster for the Vallejo Admirals says offhandedly into his mic—which broadcasts online through Mixlr and occasionally Vallejo-based Ozkat Radio 89.5—that it's a strike at the knees. Over the stadium PA system, though, PITCHf/x (through Byrnes) calls it a ball. Fitzgerald corrects what his broadcast experience has told him, and the at-bat continues. The batter fights off a few more pitches before lining a double down the third base line to tie the game. A subsequent wild pitch and a looping single later, and the Pacifics have the lead for good.

By the last few innings, the buzz of novelty has died down. The local news and sports cameras have packed up and gone home; they've got ample footage to splice together the two-minute stories that will appear on nightly broadcasts. The crowd has thinned out, the beat reporters at small local papers waiting to finish game stories and send them in by deadline. Byrnes has gone from yelling into the microphone to calmly issuing the calls—even letting his three kids take turns doing it, which elicits laughs from the crowd. They're unofficially the youngest umpires to ever work a professional baseball game.