On the Very Real Possibility That Caleb Kilian is Just a Casing Into Which New Pitches Are Poured Every Year

[Matthew Trueblood]

The Cubs righty has been very impressive this spring, not least because his arsenal seems to have been overhauled. You know, again. (Again.)

Image courtesy of © Rick Scuteri-Imagn Images

Countless times, it seems, Caleb Kilian has had enough success in the upper minors to get the Cubs organization or its fans intrigued. Then, he comes up to the majors and is a major disappointment, or he gets hurt, and he ends up in the minors again, having done nothing to actually help the Chicago Cubs win games. It's enough to make a person want, badly, to give up on him, because there's no sign that Kilian will ever cobble together the stuff, command, and mental skills necessary to turn from intriguing to valuable. However, even as one of the foremost Kilian skeptics, I have been guilty in these very digital pages of Kilian optimism.

Why does he get so many chances? Why do some (really, almost all of us, in one turn or another) keep falling for this? That, detective, is the right question.

When a pitcher comes to the big leagues, we have to go largely off their scouting reports, and what we've all gleaned from watching them in a limited capacity in the minors. There's Statcast data even in Triple A now, but not all velocity, spin, or movement is created equal, and some of the key details—arm angle, extension, spin axis, vertical approach angle, and so on—that we can readily access for big-league pitchers are much harder (or impossible) to find at that level than once a hurler reaches the bigs. If a player's stuff doesn't play when they first come up, though, we'll tend not to get excited if they go back down, have some success, and come back up, even if their raw pitching data looks promising—unless that data is also remarkably different from what it was the last time we saw them.

Kilian is the king of reinvention. No, wait, that's too simple a statement. Kilian is not reinventing himself. Kilian is, more like, just an empty vessel, and someone keeps pouring semi-random assortments of pitch shapes into him every year. It's utterly disorienting, and it makes him as hard to give up on as he is to get excited about. I really, fully, permanently have given up on Kilian, in his 2022 and 2023 iterations. I'm not sure I ever drew a final conclusion on 2024 Kilian, though I certainly didn't progress beyond my natural stance of deep suspicion. The thing is, 2025 Kilian seems to be another beast altogether.

Here's the average horizontal and vertical movement, by pitch type, for Kilian in 2022. Bigger data points mean the pitch indicated was a larger part of Kilian's arsenal.

This was the fastball-forward iteration of Kilian-bot, a ChatGPT rendition of Roy Halladay—technically, all the same pitches, but none of the feel, which it turns out was what made Roy Halladay good all along. This was the first version Cubs fans saw in the majors, when Kilian came up in May amid considerable hype and promptly squandered it all. That was a doomed experiment. He had a 10.32 ERA in three big-league starts, and his confidence was so shattered by the failure that he struggled even once he returned to the minors.

No matter. Here's his 2023 plot:

Look, you said stop relying so heavily on three fastballs, and he did, ok? This is a six-pitch guy, with more vert on his four-seam fastball and more comfort with the curveball. He even added a slider, with a fair amount of sweep to it. In the process, of course, he gave up some of the natural heaviness of his sinker, but his control of that pitch was lousy, anyway. He has the rudiments of a changeup brewing. This (or a streamlined portion of this, since the idea in the latter half of 2023 was that he would come up again as a short reliever) was the guy who tricked me into writing the piece linked above, wondering if this might work after all.

It did not. His 2023 big-league ERA was 16.88, and his ERA at Iowa ballooned to 4.56. He stopped missing bats even against minor-league hitters.

Dump it all out on the floor. Let's try rearranging the pieces and putting them back together. Here's Kilian.2024:

It's the same six pitches, technically, but it's really all different. The cutter is practically gone; he tightened up the slider into something he could occasionally throw for strikes instead. The curveball is a little more two-plane, working off an increasingly four-seam fastball shape, and he's building confidence in that changeup. This was all (or almost all) after he recovered from a major shoulder injury, so it was a minor victory just to get back onto the mound and earn another cup of big-league coffee. Minor victories are the only kind he achieved, though. His ERAs with both Iowa and Chicago were better, but he was still short on strikeouts and not throwing enough strikes to make up for the inability to consistently miss bats.

Like any good iterative programming process, though, this one learned from having gotten a bit closer last year than in previous ones. Here's what Kilian's stuff looks like so far in 2025:

Hold me back, now. Hold me back a little, because I almost want to believe! That's more ride than his fastball has ever shown before. He's letting go of the sinker and changeup, and you know why? Because he's a natural supinator, and the Cubs hired motor preferences maven Tyler Zombro last fall, and they're no longer going to try to force-fit every pitcher into a mold that requires them to work against their arm's internal wiring on at least one or two of their pitches. Instead, they're leaning harder on the pitches guys are predisposed to throw well. In Kilian's case, that's the slider and the curve, and look at those babies. The curve has a crazy amount of depth, far more than it's shown in the past. The slider is no longer even vaguely sweeper-like; it's a sharp vertical thing.

He's throwing his fastball as hard as ever, too. The slider is a much firmer offering now than when it was slurvy or sweepish. Getting rid of the cutter to embrace a truer slider sure looks good on him.

The series of catridges and chips stuffed into Kilian this year is the best one yet. I feel good saying that. And hey, good news! He's struck out 10 of the 31 batters he's faced this spring, while walking just one. That has to be good, right? Is this finally the breakout?

Well, he's also given up 12 hits (and therefore, five runs) in six innings of work. And it's spring training.

The Cubs have already technically optioned Kilian to Triple A, though he continues to pitch for the parent club in the Cactus League. He's not going to be an immediate contributor. I doubt he's even one of the top 17 or 18 pitchers the team intends to depend upon this year. Nonetheless, he has promise again. I've been kidding, all this time, mocking the idea of reinvention and calling Kilian a vapid robot. This is a game played by human beings, and the human being that is Caleb Kilian has shown admirable resiliency and openness to change. He wants to make this work, and every single year, he has shown up with a bunch of new ideas about how to make that happen.

It hasn't happened yet, and both the fan base and the organization have let go of their most cherished hopes that it'll happen. Nonetheless, until they need his 40-man roster spot for someone else, Kilian can be kept in the organization, and whatever failures of mental toughness he might have shown when thrust into the big leagues at odd times in the past, he's at least partially made up for them by being so relentless in his quest to get better. The team has enough depth, now, not to be reliant on him, but that doesn't mean they aren't pulling for him, a little bit.

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[Bertz]

If Zombro ends up being such a miracle worker he can even fix Kilian, then rip up his current contract and give him a new one with a couple extra zeroes to the end.

I'm really looking forward to closer to mid season when we can see who has been Zombro'd and where it has/hasn't made an impact.

[Transmogrified Tiger]

if Kilian is a casing into which new pitches are dumped in, does that make his arsenal a Kilianbasa

[CubinNY]

1 hour ago, Transmogrified Tiger said:

if Kilian is a casing into which new pitches are dumped in, does that make his arsenal a Kilianbasa

rounding into a good dad joke maker.

I'm a Kilian believer. 

Edited March 5, 2025 by CubinNY

[Jason Ross]

I have mostly written off Killian, but seeing that he's once again trying some new stuff gives you a little hope. There's some raw stuff there that you can always find, hopefully this iteration of Killian finds a home as something.

[Crusader]

I miss the version that was throwing 101 mph … until his shoulder self destructed.