Isiah Kiner-Falefa, high accuracy, and low precision in defensive stats

Get it out of your system now, everyone: Yes, Isiah Kiner-Falefa is a bad hitter. No, he isn’t the best use of a roster spot. Yes, it’s definitely not optimal if he’s the starting shortstop on Opening Day. If that happens, I’ll see you all at the bottom of the rubble pile from the fallen sky.

We good to go? Cool. Now that we’ve gotten that out of the way, notice that I didn’t include his defense in the above paragraph. That’s because while fans are justified in having a, how should I say, unkind view of Kiner-Falefa’s glovework, defensive stats are a bit more ambiguous. There’s certainly a fair amount of bluster behind Aaron Boone and the Yankees’ vigorous defense of his playmaking, but it’s definitely not nearly as cut-and-dry as many of us would like it to be, either.

IKF defense discourse was reunited today with Baseball Prospectus’s release of several new flagship defensive metrics, one of which described Kiner-Falefa as having the third-best “range score” among big league shortstops in 2022. The BP team did a fantastic job describing the purpose, limitations, and components of their new numbers in the lengthy explainer linked there, but you already know which part stuck out:

Sweet, just what everybody asked for: Another stat that makes it no less clear how good or bad of a shortstop IKF is. (Disclaimer: I’m lying, it actually does make it clearer, but we’re going to pretend that’s not true for another paragraph or two.) Already the cause of so much hand-wringing, it’s pretty hilarious that Kiner-Falefa might also be the poster boy for the maddening inconsistency of defensive metrics. It’s not just ambiguity, it’s polar opposite ends of the spectrum. Ultimate Zone Rating (UZR) thinks he’s been almost perfectly neutral as a shortstop since the start of 2021. Statcast’s Outs Above Average (OAA) sees him as one of the worst in the game, ranking him 37th among 42 qualified shortstops with -9 OAA in that span. Defensive Runs Saved, meanwhile, heaps praise on his output in the field, awarding him 20 over the last two years, tied for the third-most among his peers.

In spite of the uproar on Twitter, the new Baseball Prospectus metric isn’t actually saying that Kiner-Falefa was a top-three shortstop last year, as Editor-in-Chief Craig “Cruggle” Goldstein needed to clarify Tuesday evening:

Well, things do tend to make more sense when you look at the whole picture. That’s not just true of BP’s stats; Kiner-Falefa’s poor OAA isn’t a monolith either. Breaking down the directional components of the overall stat shows us that when it comes to moving back on the ball, or going to his right, or going to his left, he’s actually above average by a few outs! Going in, though? You don’t want him to go in.

Baseball Savant

Baseball Savant

Squint a little bit, watch a few highlights (or a lot of games), and OAA gives you more or less the same picture as Goldstein and the eye test: A quick fielder who can get to the ball pretty well but doesn’t have the hands or the arm to convert all of those extra chances into extra outs. In practice, it gives us a volatile fielder whose perception has been negatively tinted by a number of visible errors in big moments, but is capable of being either above or below average on the whole in any given moment. There isn’t one single stat as neat as ERA or OPS that can pin down his defensive acumen, but diving into how the sausage is made can give us enough evidence to form some kind of conclusion.

Still, it’s a lot of disparate numbers, and I don’t really know what it all means. Ultimately, it seems like what we can piece together from the spread of defensive stats on Kiner-Falefa isn’t all that different from what I’d piece together from watching games and hearing the thoughts of other observers. That’s not at all to say that the defensive stats don’t have value. The stats are polarizing because Kiner-Falefa is a polarizing player, and at the end of the day, they still typically back up more broadly the impressions we get with our eyes. They just shouldn’t be expected to provide anything close to the kind of precision we see in pitching or hitting analysis.

That’s one of the fun and beautiful things about fielding, in my opinion. Advancements in tracking technology have allowed coaches, analysts, and fans alike to strip down hitting and pitching to its very nails. But despite being subject to the same cameras and tracking tech, putting a number on fielding value remains elusive. The BP team did a very thorough job of explaining the endless array of factors that an individual fielder has no control over, and it’s a lot. Mathematically speaking, nailing down what happens after the ball is put in play is a nightmare. To some extent, conversations about defense will probably always remain a matter of knowing ball, so to speak.

Maybe that’s how it should be. More than any other phase of the game, aesthetics still matter in defense. Smooth defense is good defense, and smooth defense is pleasing to the eye. And at the same time, baseball is a slow game, and it wouldn’t be the same without the brief flashes of defensive excitement that often punctuate it. It isn’t all about gradually building up fractions of outs over the course of a six month season — it’s hard to convince me that additional positive value can’t be found in the ability to make jaw-dropping, game-stopping plays with regularity, or even more negative value in a predilection for booting routine outs? Our stats are good, but they’re not quite there yet. Part of me hopes they never will be.