Best of BP: Measuring Tags, One of Defense’s Data Voids

The runner saunters a few feet toward second base. The pitcher peeks in his direction, then turns his head to the plate. As soon as he begins his motion, the runner takes off. The catcher receives the pitch, bursts out of his crouch, then fires to second base. Got him!

Who gets the credit for nabbing the would-be thief? Historically, catchers received the lion’s share due to both old-timey stats (caught stealing percentage) and newer ones (pop time). The pitcher bears the responsibility for holding runners close and delivering quickly to home plate. Yet neither the catcher nor the pitcher actually makes contact with the baserunner, and no matter how well they do their jobs, it’s up to the infielder to apply the tag.

If the throw is accurate, tagging is an easy job, but that’s a massive “if.” When the throw is off target, tagging requires some of the most contortive acrobatics seen anywhere on a baseball field. It’s an athletic skill, which means some players do it better than others. Each player’s tagging acumen can represent the difference between safe and out, which therefore has a value that should be factored into each player’s defensive metrics… but it isn’t.

How much value do players add or subtract from tagging? There is no publicly available tagging data—or at least none that I could find. Sports Info Solutions’ Mark Simon revealed that they do track tagging misplays and good tagging plays in their data, typically available to team clients. He also asked if I planned to watch 500 tagging plays to write another article about defensive minutiae. Well, Mark, I didn’t count how many I watched this time, but let’s just call it a three-day weekend’s worth.

A lot of Baseball Prospectus articles use data to reach conclusions and share knowledge about the game. This is kind of the inverse of that. Tagging is one of the few remaining voids of data about something meaningful that happens on the diamond. What tagging metrics might be worthwhile in the public domain?

Tag Route Efficiency

Obviously, a straight line is the shortest distance between two points. Just as outfielders’ route efficiency can vary when tracking a fly ball, so can the route an infielder’s glove takes from receiving the throw to tagging the runner. Footwork and body positioning have a lot to do with setting up for an efficient tag. Here’s a smooth tag by Whit Merrifield on Anthony Rizzo from September 26:

This looks like an ordinary caught stealing—and it is! But Merrifield begins slightly behind the bag, then steps in front and leans in the direction of the throw, allowing him to use his own sideways momentum to apply a direct tag from a high toss. If he had stayed where he was when first shown on camera, it’s unlikely he would have made the catch and gotten his glove down in time to record the out. This play ended the top of the eighth in a game the Blue Jays would win 3-2 in ten innings.

Here’s an inefficient tag route by J.T. Realmuto on April 30 that allowed Brandon Nimmo to score:

This was a quick-developing play. Realmuto stuck his left shin in front of the plate in an attempt to partially block Nimmo. All it really did was prevent himself from making a clean tag. He had to swipe in a circular motion around his own knee to reach back toward the runner, and it didn’t work. If he had stood up over the plate and let the ball travel a little deeper, he might have been able to get the out.

Realmuto is at a positional disadvantage compared to an infielder. Runners heading his way can overslide because as soon as they touch home plate, they’ve scored and are no longer part of the play. More than that, he’s also an excellent overall defensive catcher who has been well-coached on the nuances of the position. That includes blocking the plate as much as possible without getting called for interference. Perhaps that coaching hasn’t caught up with the Buster Posey Rule. Realmuto did what he was trained to do, but his feeble blocking attempt put him in poor position and caused a bad tagging route. I’d love to see how catcher tag route efficiency compares to that of infielders overall, but first, that data would need to exist.

Tag Speed

Statcast has data on sprint speed, which is simply how fast players can go when they’re running all out. Tagging on bang-bang plays requires fielders to move their hands as fast as possible. On competitive tags—much like sprint speed’s competitive runs—who has the fastest hands? Tomás Nido made a quick swipe to nail Travis d’Arnaud on August 6 (d’Arnaud redeemed himself in the same game, which we’ll see a few subheadings below):

Realmuto won a Gold Glove, but he could learn something from Nido on how to make a play at the dish. Rather than trying to partially block home plate, he stood up and made the tag like an infielder. To be fair, he received a higher throw than Realmuto did above, but his body positioning still freed his mitt hand to move as fast as possible. Was he faster than an average catcher tagger? Observationally, he looks good, but without data on tag speed, it’s tough to tell.

On the other hand (pun, not sorry), Joshua Fuentes’ hands weren’t fast enough for Tony Kemp on this rundown from September 16, 2020:

Fuentes had the ball chest high with Kemp running upright, still maybe four feet away:

Kemp somehow danced around the glove, stayed in the baseline, and touched home plate. It’s an impressive display of baserunning, but Fuentes clearly didn’t react and move his glove quickly enough.

Tag Probability

I’ve watched this play two dozen times, and I still have no idea how Luis Urías clipped Brendan Donovan’s heel on June 20 (the original safe call was overturned on review):

Sorcery! It’s the Jim Edmonds backward diving catch of tags! Incorporating the runner’s speed and distance from the base when the fielder catches the ball, as well as the distance from the fielder’s glove to the runner, should allow us* to calculate tag probability for any play. I don’t know what the tag probability would be on the above, but it’s pretty darn low. This play’s 11% WPA made it the second-most important event of the game.

I don’t need an abacus to tell you that the probability of Gary Sánchez tagging Jonathan Villar on September 10, 2021, was 99.9% (the original out call was overturned):

This was a bad baserunning decision bailed out by an inexplicably poor tag. Sánchez was in an ideal position to make the tag with Villar still 20 feet away from home plate.

For some reason, he rose out of his crouch and tried to daintily pet Villar on the top of the helmet as the runner’s foot slid in underneath and touched home. This is the tagging equivalent of losing an easy fly ball in the sun. Even the most ardent Sánchez supporters couldn’t defend this, and it’s at least some small part of the reason why he was traded to Minnesota the following offseason.

Drop Rate

The three tagging metrics above mostly have to do with positioning and glove movement. Before any of that can happen, the fielder must first catch the ball, which can be easier said than done. Let’s bring back d’Arnaud from that August 6 game, this time on defense as Pete Alonso tries to score on a hot smash to third base:

Alonso was safe on the play, but this is some outstanding gymnastics from d’Arnaud to 1) catch the high throw, and 2) apply a quick tag without dropping the ball. The original (overturned) call was out, which wouldn’t have been possible without a highlight-reel defensive play.

Here’s an example of a play from way back on July 17, 1990, in which Mike Macfarlane failed to catch the ball twice:

Bo Jackson couldn’t make the catch in center field, giving Deion Sanders an opportunity for an inside-the-park home run. Macfarlane missed the original throw, but the collision propelled Deion over and past the plate. Mel Stottlemyre, Jr. backed up the play and flipped to Macfarlane for a second try, but he dropped it once again. He would’ve gotten the out had he secured either one of the throws. 

Don’t feel bad for Bo. He went 3-3 with three home runs that day playing both his and Deion’s second-best sport. Baseball was Macfarlane’s bread-and-butter, though, so he probably should’ve caught the ball.

Overslide Tag-Hold Rate

Before umpire calls could be reviewed, oversliding the bag was kind of like the neighborhood play. By the letter of the rulebook, the runner should be called out for losing contact with the base, but it was rarely called an out. These days, it’s a somewhat regular occurrence, especially after a review.

Sometimes, it’s not enough to apply a quick tag on a runner—fielders have to keep their gloves on them in case they slip off the base. Rougned Odor demonstrated how it’s done against Jean Segura on June 12, 2021:

Segura beat the throw but clearly slid past second base. Odor kept his glove on Segura’s foot for the out. Speaking of the throw, I’m not trying to repeatedly pick on Sánchez. Part of my super-advanced research methodology was to search “overslide” on Twitter, and the best example I found just happened to show him flailing at a baseball on the ground like it’s a greased-up ball bearing. Anyway, guess who stars in this next clip from June 20, 2021?

When you woke up today, you didn’t realize how much you needed to see Sánchez repeatedly being a baseball weirdo, but I’ve got you covered. No one knows why he didn’t slide into third, but he was safe… so it worked out, sort of?? Matt Chapman probably could’ve tagged him if he had gotten off his ass at any point during the play. Sánchez overran the bag, but Chapman couldn’t put the tag on.

Tagging all the way through the play is part of an infielder’s job and a great way to turn safe into out. Data that shows how well they pick off runners on overslides remains an unquantified aspect of defense.

Call Overturn +/-

Many of the plays above involved a replay review that overturned the call on the field. I don’t know if tagging plays comprise the majority of reviewed calls, but they’re definitely a significant chunk of them. Would a plus/minus system for overturned calls mean anything? From what little I know of basketball and hockey—sports where plus/minus is prominent—it’s basically their equivalent of the RBI. When applied to tagging review calls, it might show an infielder’s movements are quicker than the well-trained naked eye of an umpire. Or it might just be trash. We can’t know until there’s real data!

Here’s what a plus looks like, courtesy of Nico Hoerner tagging Austin Nola on May 10:

This is also a great example of an overslide tag-hold. Nola easily beat the throw and the ump called him safe, but he popped up and off the base for just a moment. It’s a clear out on further review.

If you’ve made it this far into the article, you can probably predict who’s going to look bad in the counterexample. Hint: his name rhymes with Shmary Shmánchez:

Guess who? No, it’s not Ryan Jeffers. On August 7, Whit Merrifield tagged from third on a fly ball (not that kind of tagging, the other kind). Sánchez definitely got the tag down and the runner was out. In fact, his foot never reached home plate at all because it was completely obstructed. As it turns out, that’s against the rules. The play was overturned and Merrifield was safe because Sánchez illegally blocked the plate.

***

None of us knows how valuable of a defensive skill tagging is. It’s worth somewhere between zero runs and all of the runs, and it’s probably much closer to the former than the latter. I don’t know if the proposed metrics above would shed that much light on the subject or not, but right now, it’s an aspect of baseball completely shrouded in darkness. Until we have data, all we can do is estimate. For Sánchez, maybe that’s for the best.

* By “us,” I mean someone smarter than I am.

Thanks to Mark Simon for research assistance including sending me the awesome Urías tag.