Tyler Glasnow’s New Groove

Did you know that Tyler Glasnow was once a Pirate? Yes, like every other baseball writer in existence, I’m contractually obligated to point that out in any article I write about him. Good news, though — I promise that’s the last time I’ll mention them in this article, because I want to talk about something that Glasnow has done this year to add a much-needed wrinkle to his game.

The Glasnow of the past few years was a two-trick pony, if such a thing exists. Trick one: a fastball that sits around 97 mph and touches 101 when he needs it. It doesn’t stand out for exceptional rise or transverse spin efficiency, but it doesn’t need to. Glasnow’s velocity and extension make for a flat-planed, dynamic pitch that both misses bats and induces weak contact.

You already knew that, because you can’t watch a Glasnow appearance without marveling at the graceful explosion of the pitch, seemingly catapulted by his smooth delivery. Here, watch him overpower J.D. Martinez:

Ah, what a joy to watch.

You’ve likely seen Glasnow’s second trick, as well: a big-bending, 12-6 curve that appears to warp space and time. There’s no way a pitch thrown that hard should break so much; per Baseball Savant, it has five more inches of drop than the average curveball thrown with similar velocity. This isn’t one of those pitches with just enough wiggle to miss the big part of the bat; this misses the bat entirely, and by more than a hair.

What’s more, the curveball spins in the exact opposite direction of the fastball. That makes it harder for batters to discern between the two, and you really don’t want to gear up for 97 up in the zone and then try to hit a curveball that falls 42 inches more on its flight home than the fastball would have. One more GIF? One more GIF:

Cool, great, we’re all caught up to Glasnow as of 2020. He threw a fastball and a curve, and the two paired masterfully. That was it! Oh sure, he threw the odd changeup — 63 in all of 2020, and 31 the year before — but that’s more of a technicality than a third pitch.

How much does that matter? It’s a matter of opinion, but you could pluck out some data points that suggest Glasnow didn’t suffer overmuch from a lack of diversity. For one, he led the majors in putaway percentage, the rate at which he turned two-strike pitches into strikeouts, last year. It doesn’t seem like batters were able to predict and lay off his pitches in high-impact situations. That list isn’t one you can fake your way onto, either:

Putaway% Leaders, 2020
Pitcher Putaway%
Tyler Glasnow 30.2%
Shane Bieber 28.4%
Corbin Burnes 28.4%
Framber Valdez 27.7%
Dinelson Lamet 26.2%
Aaron Nola 27.7%
Jacob deGrom 26.2%
Joe Musgrove 26.1%
Zac Gallen 26.1%
Dylan Bundy 25.9%

There’s also the matter of his performance. Between his 2018 Rays debut and the end of 2020, he compiled a 3.32 ERA and 3.40 FIP thanks to his 33.3% strikeout rate. That ranks among the best 25 starters in baseball on. Maybe the two pitches aren’t such a big deal.

On the other hand, Glasnow was the very picture of inefficiency. He averaged just over five innings per start in that span. It’s basically a math problem: Glasnow doesn’t often throw his curveball in the zone, but he can’t turn into a fastball-only pitcher when behind in the count — it’s a great fastball, but major league hitters are great at baseball, and they don’t generally miss fastballs in fastball counts from a pitcher who has no option but to tangle with them.

That means he has to mix in some amount of curveballs, but given its hellacious break, that leads to a good amount of pitches outside the zone. That puts a lot of pressure on Glasnow to start counts ahead — opponents have compiled a wOBA 140 points higher against him when ahead 1-0 as compared to behind 0-1, 30 points higher than league average.

To reiterate, none of this means that Glasnow wasn’t an effective pitcher before this year. He was one of the top 25 starters in baseball on a rate basis! He doesn’t throw a particularly high number of pitches per batter faced, and while his ahead/behind splits are elevated, they aren’t ghastly.

There’s the matter of times-through-the-order splits, and it’s easy to imagine that a pitcher with two pitches might struggle against hitters as they see those pitches more often. Two counterpoints: Glasnow has been better on the third time through than the second (in splits too small to be meaningful), and the Rays let him face at least one batter a third time in all but one of his 11 starts. He’s not Max Scherzer out there, but hey, lots of people fall into the general category of “not Max Scherzer.”

Anyway! We’re 800 words in, and I haven’t even gotten into the meat of this article yet: Glasnow is a two-pitch pitcher no longer. He added a slider to his arsenal, and he’s thrown it roughly a third of the time this year. It isn’t anything fancy so far, and it hasn’t had to be; batters need to gear up so hard for the two headliners that the slider befuddles them:

I cherry-picked an example, but this use case — a pitch he can throw in or around the strike zone that isn’t a fastball — is exactly what was lacking in his old arsenal. The exact shape of the pitch isn’t nailed down yet — it overlaps in velocity with his curveball, and while on average it has two-plane break, there’s still a good deal of variation from one pitch to the next, hardly surprising as he gains feel for it.

One thing is for sure: this isn’t the slider/cutter hybrid so many pitchers have added in recent years, despite velocity pushing 90 mph at times. It drops relative to spin-less motion, where those hybrid pitches have no drop or even slight ride. He throws it with a distinct axis as compared to his curveball — more sidespin, though still plenty of topspin — and with a similar spin rate. It feels more like a curve/slider hybrid than anything else, which makes sense for someone with Glasnow’s feel for breaking stuff.

Thus far, the raw numbers on the pitch are unremarkable. Batters are swinging at about half of the sliders he throws, an average rate. When they swing, they’re missing about a third of the time, ever-so-slightly less frequently than hitters miss an average slider. He throws it in the zone half the time — you guessed it, roughly average.

So, uh… what? Glasnow has two absolutely premium pitches in his arsenal. He’s shelving them — largely the curve, which he’s thrown only 11% of the time so far this year — in favor of a serviceable slider. This is supposed to be a good development?

It is! There might not be a conclusive body of research about the benefits of adding pitches, but so far, both of Glasnow’s other pitches appear to play well with the slider. He’s thrown 18 curveballs this year — and gotten seven strikeouts on those pitches. None of those have been thrown when he’s behind in the count, and why would they? It was always a pitch to throw when ahead. Glasnow simply had no other tools before. Subtracting the curveballs that he threw in suboptimal situations flatters the remainder.

Meanwhile, having another credible pitch he can locate in the zone when behind in the count protects his fastball. Last year, if a batter got ahead in the count, Glasnow went to the fastball 84.4% of the time. That didn’t stop him from throwing it by them, because it’s an incredible pitch, but it’s not like he was fooling hitters with his pitch selection. This year, he’s down to 70% fastballs when he’s behind.

It’s too early to look at count-based splits — honestly, it’s almost always too early to look at count-based splits, as they take forever to become reliable — but try this hilariously small-sample statistic on for size: in 19 1-0 counts, Glasnow has gotten a strike 11 times, a 57.9% rate. In his career before this year, that stood at 48%. For a guy with such lethal strikeout stuff, favorable counts are worth their weight in gold, and his slider is a way to get there with greater frequency.

Will this experiment work out? I have no clue. There are signs pointing both directions. Glasnow’s walk rate has plummeted this year, though of course he’s only made two starts. On the other hand, the slider isn’t doing what you’d hope in at least one way — batters aren’t chasing it much (28% of the time), but they are swinging a lot when he ventures into the zone (74%).

Want some more conflicting signs? Per our pitch weights, his slider has been tied with his fastball as his best pitch so far this year. Easy! What a good decision to throw it. But most of that positive value has been accrued on balls in play — volatile readings, to say the least. And batters are making more contact on out-of-zone pitches overall, even though the slider theoretically helps the curveball play up on that front. It’s a puzzle!

In truth, I’m not sure what to make of Glasnow’s new pitch. Glasnow has always been a study in logical extremes. You know how analysts are always saying “throw your best pitches more”? That’s exactly what he already did. He has two absolutely dominant offerings, and he threw them to the exclusion of any other pitches. Now he’s not doing that, and the results are intriguing.

I haven’t drawn any new conclusions about the pitch yet, and truthfully, I doubt Glasnow has either. He’s only used it in two games, and batters are adjusting to the new pitch as much as he is. Seeing its usage evolve will be fascinating, and the pitch certainly still has some growth left — it was literally created in a lab during spring training.

Given Glasnow’s feel for his curveball, there’s a good chance that he keeps improving the pitch, adding bite and refining its usage. Selfishly, though, I hope it doesn’t improve. I love the experiment of one of the game’s best two-pitch pitchers adding an ordinary third one. I don’t know how it will all shake out, and I love that I don’t know. Glasnow’s starts are appointment viewing, and watching him test out a new theory live on air is a fun subplot in an already-exciting season.





Ben is a writer at FanGraphs. He can be found on Twitter @_Ben_Clemens.

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Cave Dameron
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Cave Dameron

Are you saying he looks like a llama?