Gen-Z Is Killing the Curveball

Mates, I come to you at present to alleviate my soul of a burden I’ve been carrying. I’ve been harboring a cranky, irrational, previous man opinion, and worse nonetheless, I’ve been mendacity to you about it.

Again and again, whereas evaluating pitchers, I’ve praised the slider. Dylan Stop’s slider? Unimaginable. Andrés Muñoz, Chris Sale, whoever. Within the kayfabe my place calls for, I have to reward a slider that will get outs. However my coronary heart isn’t in it. I’m awed by the slider’s effectiveness the identical approach I’m awed by the voraciousness of a swarm of locusts.

Deep down, I detest the slider. It’s a crude instrument, with not one of the curveball’s grace or the changeup’s playfulness. The curveball is a calligraphy brush, all swooping strains and fantastic management. The changeup is a Blackwing pencil, wealthy and exact, its marks right here one second and gone the subsequent.

The slider is a crayon.

It’s a crude, imprecise instrument, the proper pitch for this second in historical past, an age of postliterate maximalism in all areas of life, baseball included. There’s a (most likely apocryphal) story concerning the Purple Military at Stalingrad, depicted memorably in Enemy on the Gates: Troopers would arrive on the entrance to search out that there weren’t sufficient rifles to go round. So the Purple Military officers would ship unarmed males to the entrance and inform them to take a gun from a lifeless comrade.

The fashionable main league workforce have to be restrained by statute to an eight-man bullpen, and the trail to the playoffs regularly leaves that many exhausted arms on the injured checklist. If the GM is Marshal Zhukhov, the slider is the Mosin-Nagant. Don’t be alarmed. A bullpen spot will turn out to be obtainable quickly.

Maybe I may not discover the slider so objectionable, so noisome, if it weren’t consuming its extra lovely, venerable sibling: the curveball.

This season, simply 8.12% of complete pitches thrown have been curveballs, which is the bottom mark of the pitch monitoring period. The league-wide curveball fee is down virtually precisely a 3rd from its all-time excessive, which was as latest as 2020. (These figures embrace all pitches within the curveball group, so true curves, knuckle curves, and “gradual curves,” in response to Baseball Savant, whereas the slider group consists of sliders, sweepers, and slurves.)

Now, I known as my hatred of the slider and love of the curveball an “previous man opinion” as a result of having a fierce normative opinion based mostly on completely no empirical proof in any respect has lengthy been the province of the previous man. (Whereas scripting this sentence, I ever so briefly imagined a model of Archie Bunker who lived throughout the age of 24-hour cable information and have become so frightened I needed to rise up and go for a stroll.)

However that is additionally an previous man opinion as a result of, increasingly more, the curveball is an previous man’s pitch. Not solely is the curveball reducing in reputation, older pitchers are accounting for a better share of these few curveballs that do get thrown. I took the inhabitants of pitchers and sorted it into 5 buckets by age: 23 and beneath, 24 to 27, 28 to 31, 32 to 35, and 36 and up.

Over the previous 17 seasons, the typical age of the key league pitcher, sorted by workload, has shifted barely older. For the primary 16 seasons, probably the most populous bucket in each season was the 24-to-27 age group; within the late 2000s, that group threw about 300,000 pitches a yr, whereas the 28-to-31s threw lower than 200,000 pitches a yr. However that hole narrowed steadily all through the 2010s and into the 2020s:

This season, we lastly noticed convergence. The 28-to-31s have thrown about 4,600 extra pitches up to now this season than the 24-to-27s. And whereas the proportion of pitches thrown by the 32-and-up group held regular at round 20% from 2008 to 2022, the previous two seasons, these graybeards have thrown a couple of quarter of the league’s complete pitches.

So cancel that botox appointment: 31 is the brand new 24.

Initially, I used to be taking a look at a fairly appalling shift in age profile for curveball customers. In 2008, 52.6% of curveballs had been thrown by pitchers 27 and youthful; this yr, that’s all the way down to 37.7%. However these uncooked numbers exaggerate the development, as a result of the league as a complete is getting extra work from older pitchers.

To get a extra practical appraisal of the age profile of curveball customers, we have now to check the proportion of the league’s curveballs thrown by every age group to the proportion of complete pitches thrown by every age group.

At this level, I noticed that I used to be in search of one thing that may very well be expressed the identical approach as a plus statistic, like wRC+ or OPS+. So for annually, I took every age group’s curveball utilization fee and in contrast it to the league-wide curveball utilization fee, utilizing 100 as a baseline. In 2013, 32- to 35-year-olds threw 13.52% of the league’s curveballs and 13.51% of its complete pitches. So for that season, that age group will get a Curveball+ rating (for lack of a greater title, it’s not like anybody’s ever going to make use of this nomenclature once more) of an excellent 100. Cohorts that throw extra curveballs than common get the next rating; people who throw lower than the league common get a decrease rating.

To make the outliers extra apparent, I’ve marked scores beneath 90 in blue, scores between 111 and 120 in orange, and scores over 120 in crimson:

Outdated guys have thrown a disproportionate share of curveballs over the previous six or seven years, and a vastly disproportionate share for the reason that pandemic.

And right here’s the place issues get actually scary. As soon as we’re splitting hairs this fantastic — with 36-and-over pitchers in a single season, throwing a single pitch kind — we’re not speaking about that many pitches. That 178 in 2022 is simply 5,823 curveballs, out of a complete of 717,945 pitches thrown league-wide over your complete season.

So what made the curveball take off a lot amongst previous pitchers within the early 2010s?

I can really pinpoint the precise date all the pieces modified: November 12, 2019. That’s the day Charlie Morton turned 36, and aged into that final bucket. Regardless that Morton solely began 9 regular-season video games in 2020 and went very mild on the hook by his requirements, he accounted for 16.4% of all curveballs thrown by pitchers 36 and over in 2020.

And what accounts for the sharp decline from 2023 to 2024? Wealthy Hill hasn’t pitched this season. Since 2020, Hill and Morton have accounted for a couple of third of the Outdated Man Curveballs within the league yearly:

These two are stemming the tide. They usually’re not going to maintain going perpetually. A one share level drop within the league-wide curveball fee is about 7,000 pitches a yr. If Hill and Morton are good for two,000 curveballs a yr, changing them with slider jockeys goes to have a measurable influence on this endangered species.

And the inhabitants is simply getting older. Listed below are the ten highest curveball charges (mixed curve and knuckle-curve) amongst pitchers with at the least 70 innings this yr:

Reducing the innings threshold doesn’t make issues significantly better; the league chief with a 50-inning minimal is 35-year-old Drew Smyly, who’s thrown his curveball 47.3% of the time this season.

Curveballs, then, are like ankle socks and response GIFs: They’re going to die out with the Geriatric Millennials, leaving us to endure by a dystopia the place one-inning fastball-slider guys are grown in vats by the thousand, then used up and discarded. The artists, the technicians, the Mortons and Hills, aren’t lengthy for this league. I pity the generations to come back.