A Rookie Robot Umpire Takes The Field

IRA FLATOW: There is one certain sign that spring has sprung and I’m talking baseball. If you listen to this show, you know how much I love baseball. And the geek in me loves to understand the science and the technology behind it because the beauty is in the details.

I bring all of this up because in addition to the new rules in baseball, like the pitch clock, the ghost runner, and extra innings, now, comes another wrinkle, the AI umpire. In some spring training games, baseball has been testing a robotic system to verify calls made by the home plate’s umpire. Was it a ball? Was it a strike?

Well, here to explain the tech and how it might change the game is Davy Andrews, a musician and baseball writer. He’s contributing writer for FanGraphs. Welcome to Science Friday.

DAVY ANDREWS: Thank you very much for having me, Ira.

IRA FLATOW: Let’s talk about explaining this. How does the system work? It doesn’t call every pitch, does it?

DAVY ANDREWS: No, although they have tested that in Triple-A. And right now, it’s a challenge system that uses hawk-eye cameras, which are the same technology that’s used to challenge line calls in tennis. When a batter or a catcher or a pitcher disagrees with the umpire’s call, they have the chance to tap their head, which has become the signal, and they quickly check to see if the ball hit the strike zone, according to those Statcast hawk-eye cameras.

IRA FLATOW: Yeah, I’ve watched some of the spring training games, and what happens is there is a white computer-generated strike zone put up on the screen, and you look to see whether the ball touches the white area or not, just like it touches the line in tennis or not, right?

DAVY ANDREWS: Exactly.

IRA FLATOW: And the thing I have about it that bothers me is that this strike zone is two dimensional, but the real strike zone is three dimensional, right?

DAVY ANDREWS: Absolutely. The rule book strike zone, which is the one even now in spring training that umpires are calling, is the area over home plate, which is pentagonal, and it’s between the player’s knees and the midpoint between their belt and their armpits. And so it’s a pentagonal prism. It’s a volume, as opposed to just a two-dimensional rectangle, like you said. So there’s a little disconnect here.

IRA FLATOW: Does this get in the way of calling balls and strikes?

DAVY ANDREWS: I mean, the answer is yes and no. So they have tried at previous iterations were three dimensional, and they found that the strike zone was a little too big. And sometimes there are pitches that every pitch drops on its way to home plate, because of gravity, and many of them also, because of the spin that the pitcher imparts onto the ball.

And so there are ways for the pitch to dip and touch the back of home plate or maybe the front of home plate or the sides, but to exit the strike zone before it hits that one rectangle, which is located right in the middle of the plate. So technically, the umpires and the robots are calling two completely different zones. They just overlap a great deal.

IRA FLATOW: Is that right?

DAVY ANDREWS: So the rule book zone, like I said, is knees and the midpoint between belt and armpit. The robots are doing it. It’s a percentage of the player’s height, so it’s actually just over a quarter of their height. It’s no longer your knees or your shoulders or anything like that.

All the players in Triple-A last year, hundreds of players shrank by several inches.

IRA FLATOW: You mean they leaned over to make their strike zone small.

DAVY ANDREWS: You can’t do that anymore. I’m sure people remember Rickey Henderson, or Pete Rose would crouch into a ball, basically, to give themselves the smallest possible strike zone. The robo zone doesn’t appreciate that.

So in the minors last year, hundreds of players magically got much shorter because they didn’t want to be charged for a bigger strike zone when they didn’t actually have one.

IRA FLATOW: Oh, that is funny. A lot of purists are not going to this.

DAVY ANDREWS: Absolutely.

IRA FLATOW: Is there a lot of talk, a lot of disagreement about it being accepted?

DAVY ANDREWS: I think there are places where even if you’re not necessarily a hardcore purist, there are parts to argue with. There are certain players who don’t like it. And the reason I ended up writing about it is because Max Scherzer, who is a very respected player and a Hall of Famer, or will be a Hall of Famer five years after he retires, he brought it up.

And he made a very real point that we’re humans, and maybe it just makes sense to be judged by humans. That said, the challenge system has gone over remarkably well because it’s quick and it’s accurate. It seems fair, and it doesn’t cut out a lot of the things that people like.

The thing that I worry about is that there’s a huge value in framing for a catcher and catching the ball in such a way that you make a ball look like a strike. Or you just keep a ball that is a strike from appearing like a ball. It’s not necessarily fooling the umpire, but it’s a very important part of a catcher’s job, and it’s a very important part of the game, traditionally.

And If they were just to switch over to a full, automatic zone, that would disappear, and catcher’s job wouldn’t really matter anymore, and that seems a lot less fun to me.

IRA FLATOW: Yeah, we’ve had challenges, where you can challenge ruling on the field. And then they have to go away. The umps huddle. They get their headsets on. How is this different than that?

DAVY ANDREWS: Well, so this is different because it’s done all by cameras. It’s technology making this decision. And according to Hawkeye’s press releases, it’s accurate down to just over 2 millimeters. So it’s not perfect. And I would ask people to keep in mind that normal umpires, according to MLB’s data, get the call right 93% of the time.

And even on balls that are close to the edges of the zone within one baseball’s width, they’re still right 82% of the time. So they’re already very, very good. But this is a little more impartial and objective.

And it is more accurate. There’s no way for a human eye to be as good at this as a series of high-speed cameras.

IRA FLATOW: How soon do you think until we see it every day?

DAVY ANDREWS: I mean, it’s not going to happen this season. I think it’s possible that it will be as early as next season. I think it’s more likely that the collective bargaining agreement is up after the 2026 season. So I suspect that it will be rolled in the 2027 season, after all those changes happen.

IRA FLATOW: Well, as a baseball fanatic, I’m very much in favor of this, especially in critical areas and critical times, critical pitchers in the game, right? You want to be able to get it right.

DAVY ANDREWS: Sure. Well, I was told that you were a Mets fan.

IRA FLATOW: Yes.

DAVY ANDREWS: And I’m sorry. I actually just have an article coming out. Your catcher, Francisco Alvarez, who just went down with an injury. But he is an excellent framer. And so if you’re hoping that the Mets do well once they get him back, he’s the kind of guy who would make you not want to robo zone, because he is good at making pitches look like strikes and getting those borderline calls.

IRA FLATOW: Well, Thanks a lot, again, for putting another stab into my Mets fandom, like everyone else does. Thank you, Davy, for taking time to be with us today, and good luck in your writing.

DAVY ANDREWS: It was my pleasure. Thank you very much, Ira.

IRA FLATOW: Davy Andrews is a musician and baseball writer, a contributing writer for FanGraphs. He’s based in Brooklyn.

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