While You Sat in Awe of His Fastball, Jacob Misiorowski Broke Out a True Slider Monday

It was hard not to give all one's attention to Jacob Misiorowski's fastball on Monday. There's never been such an overpowering arm; he's bullying hitters with an utterly unprecedented heater. He threw 59 pitches with a perceived velocity (the raw velocity, plus an adjustment for his elite extension, releasing the ball about 12% of the way from the pitcher's mound to home plate) of 102 miles per hour or more in the game, sliding him into third place all-time in such pitches. He's only one behind Jordan Hicks for second—all this in less than a year in the majors.

Amid his 7 dazzling innings of two-hit, one-run, 12-strikeout ball, though, Misiorowski did something else worth noting on Monday: he mixed in a true slider. His breaking stuff stretched across an unusually continuous spectrum of speed and movement, becoming impossible to contend with for Cardinals batters just trying to cope with 103 miles per hour.

Over the winter, our Jack Stern wrote about the fact that Misiorowski's pitch often labeled a slider is really a cutter. It's often come in at more than 95 MPH, and it hasn't had the depth of movement—in particular, the separation of movement from the fastball—of a true slider. In several key respects, the pitch is much more like a cutter than a slider.

That was true last year, and it's remained true for most of this season. Here's what his movement plot for his antepenultimate start against the Padres looked like.

There's actually more separation in movement between the fastball and the so-called slider than between the slider and the curveball, in this image, which invites you to think of the in-between pitch as a slider. In truth, though, that's only because his curveball is such a tight, power pitch. Most of those mustard-yellow pitches in the center of the plot are pretty clearly cutters, especially when you factor in the mid-90s velocity. However, the distribution there did preview something, as we'll soon see.

Here's the same plot for his start against the Cubs last week. As you can see, the distribution of that "slider" is much smaller; it was unequivocally a hard cutter that night at Wrigley Field.

Now, though, compare each of the above images to this one, showing the movement of his stuff on Monday at Uecker Field.

At a certain point, Statcast's spirit breaks, and it gives up a little bit. Is a pitch that comes in at almost exactly 90 miles per hour, but with more depth than any slider you've seen lately, really a curveball? It's hard to say. The computers aren't designed to deal with anything quite this freakish. It tagged a couple of pitches that might have been extremely high-powered curves as sliders; it tagged a couple of could-be sliders as turbo curves.

Either way, though, look at how wide and uniform the distribution of his breaking balls' movement was. Indeed, there's a blend from curveball to slider, but none of what you'd readily call a cutter, as there was even one start ago.

Pitch-tagging trouble could be introducing distortions, but it sure looks like Misiorowski threw the slowest average sliders of his season Monday—rivaled only by that game against the Padres earlier this month.

When two pitches' velocity is up and one is down in a given outing, it signals some kind of intentional change. So does the fact that Misiorowski's slider had a higher spin rate than usual on Monday, despite the lower velocity. (Those two numbers are usually strongly correlated, and his curveball's average spin rate is lower than his slider's, so the higher spin rate on the slider suggests that few or none of them were mistagged curves.) Misiorowski has also never had so much vertical depth on his slider:

Or so much glove-side movement:

There really seems to be a new pitch in the mix, here. It's likely that Misiorowski is still throwing that hard cutter some of the time, but he now seems to have a feel for a slider that fits between the cutter and his curveball in terms of both movement and velocity. That's just unfair, but it's true.

This new pitch didn't actually miss any bats for Misiorowski on Monday. However, he got multiple weak swings and feeble pieces of contact on it, leading to easy outs and upping his already impressive efficiency. If this turns out to be a durable new dimension to his game, watch out. Already, in his last six starts, he's allowed zero extra-base hits. If this change locks in for him, a no-hitter is right around the corner.