Kirby Yates Is Making Highly Specific History

I’ve made no secret of my longtime admiration for Rangers reliever Kirby Yates (formerly Braves reliever Kirby Yates and Padres reliever Kirby Yates), but what he’s doing now even surprised me.

Yates entered Tuesday night’s contest against the Boston Red Sox with an ERA of 1.04; that mark is second among big league relievers, behind only Emmanuel Clase (another favorite of mine). It’s also a career best for Yates, which is more surprising than it would be for most pitchers. Yates already has a season with a microscopic ERA on his CV: 2019, when he posted a 1.19 ERA in 60 2/3 innings, with a strikeout rate of 41.6% and a walk rate of 5.3%. Pitchers who produce even one season of that quality are vanishingly rare; pitchers who produce two are almost unheard of.

The following fun fact represents a mélange of arbitrary cutoffs and endpoints, but that doesn’t make it any less fun: In MLB history, there have been just 41 individual instances of a reliever posting an ERA of 1.25 or better in a season of 40 appearances or more. Three of those seasons — by Yates, Clase, and Andrés Muñoz — are currently in progress.

How many pitchers have done it twice? Just three. Mariano Rivera only did it once. So did Jonathan Papelbon, Eric Gagné, Rollie Fingers, and Dennis Eckersley. If Yates hangs on until the end of the season, he’ll join Craig Kimbrel and Wade Davis as the only relievers with multiple seasons under 1.25. And Kimbrel and Davis did it in back-to-back years; Yates would be the only pitcher to reach that pinnacle once, miss multiple seasons, then climb all the way back to the summit from sea level again.

As luck would have it, Yates and the Rangers are currently in Boston, where David Laurila had the opportunity to inform the veteran righty about the historic pace he’s on. Yates said that while he doesn’t like to know his numbers during the year (which is fair enough; I almost told David not to say anything for fear of jinxing Yates), “If it happens, it happens. It’s great…But the hard part is that there are six weeks left in the season. Being a bullpen guy, a lot can happen in six weeks.”

Sure enough, there’s no room to relax when the standards are this high. As of this writing, Yates has allowed five earned runs in 43 1/3 innings. Let’s say he ends the year with 60 innings pitched, which is about what he threw in each of his past three healthy seasons. In that case, Yates would only be able to allow 2.9 more earned runs this year if he wants to stay under his previous career best for ERA. That’s not a lot of margin for error.

Closer is the ultimate results-based job. Even a closer who keeps local cardiologists in business by walking the leadoff batter every game will end up being treated as a beloved, if slightly eccentric, figure if he consistently converts the save. And when you’re talking about the level Yates is operating on — and did in 2019 — any attempt to find evidence of flukiness just comes off as nitpicking. Nevertheless, part of what made Yates’ 2019 season so impressive was how he did it.

There are, broadly speaking, two types of closer. The first has such nasty stuff — a 100 mph fastball, an antisocial knuckle-curve — that onlookers say, “How is he doing that?” This is, broadly speaking, the Kimbrel archetype.

The second relies on pinpoint command to miss barrels, sometimes only requiring one pitch to save 30 games a year for 10 years. This is Rivera, Eckersley, Kenley Jansen, and so on. These guys don’t just rack up strikeout numbers, they rack up huge strikeout-to-walk ratios. So when Yates, in 2019, struck out almost eight batters per walk and posted a FIP of just 1.30, that was almost as impressive as his surface numbers.

This year, not so much. Yates went from the 90th percentile for walk rate in 2019 to the 10th percentile in 2024. His FIP is all the way up to 2.14 this year! That’s not really concerning for three reasons: First, there have been 113 seasons in major league history where a reliever has posted an ERA of 1.50 or better. Said reliever outperformed his FIP in 107 of those seasons, more than half of them by a full run. And two of the six relievers who underperformed their FIP did so by just 0.01 runs. Second, Yates is still in the top 10 among qualified relievers in FIP this year. Third, he’s doing to hits this year what he did to walks in 2019.

Yates was already 32 in 2019; he’s 37 now. Between his advancing years and the nearly three full seasons he spent on the IL, you’d expect him to have made some adjustments. Maybe he’s lost some velocity or added a third pitch, or changed his mechanics. And actually, he has dropped his release point by about two and a half inches, but without similar gains in extension or horizontal release angle.

Either way, once the ball leaves his hand, it’s moving the same way it did in 2019:

Same two pitches, basically the same proportions, similar velocity and movement profiles. But while Yates’ ERA is unchanged, his walk rate has more than doubled since 2019, while his opponent batting average has dropped more than 50 points from its already sub-.200 starting point. Yates is on track for one of the 10 lowest opponent batting averages in history for a reliever with at least 40 innings pitched.

In 2019, Yates was barely in the top 20 among relievers in opponent batting average. He was behind Oliver Drake, Tyler Webb, and Trey Wingenter. Brandon Workman — remember him? — had Yates beat by more than 60 points. Brandon Workman!

So how does throwing the same pitches in the same proportions lead to the same success in such dissimilar ways? Let’s shift our focus to where Yates is throwing it and what hitters are doing with it:

I don’t know if you’d want to call it a subtle difference in where Yates is working, but there is a difference. In 2019, he generally threw his fastball in the zone — anywhere in the zone, really, with his splitter along the bottom edge of the zone. In 2024, there’s more vertical separation: Fastball up in the zone, splitter down. Sometimes way down; not only is Yates only throwing about a quarter of his splitters in the zone, when he’s throwing that pitch low, he’s really burying it:

So I guess it’s not that surprising that he’s walking a ton of hitters. In 2019, Yates’ splitter was his best pitch. According to Baseball Savant’s run value, Yates’ splitter was one of the 10 most effective individual pitches in the league among offerings that were used at least 250 times. His four-seamer was very good, but nothing spectacular.

This year, those values are just about reversed. In 2019, Yates’ splitter was +3.5 runs per 100 pitches and +15 in total, while his fastball was +1.3 per 100 pitches and +8 in total. In 2024, Yates’ splitter is +1.1 per 100 pitches and +3 in total; his four-seamer is +3.1 per 100 pitches and +13 in total.

In other words, by changing his default pitch locations, Yates has sacrificed walks to avoid hits and changed his most effective pitch from a splitter low in the zone to a fastball up. Same guy, same two pitches, same results, very different paths to getting there.