Nate Pearson is in a New Place, and He's Also in a New Place

Since acquiring Nate Pearson in their first move of July, the Cubs have used him relatively sparingly. He pitched in each of the first two games of this week's series against the Guardians, but that was after a full week off. In his first fortnight in the organization, he only pitched three times. That's because the Cubs had some ideas about how to solve the command issues that have plagued him during his career, and while it's too early to draw wild conclusions, there are some encouraging results in that area.

Here's a pitch Pearson threw in June, when the Blue Jays visited the Guardians.

Here's one he threw this week, in the same ballpark and from the same outfield camera angle.

I bet you can spot it right away, but in case you missed it: look for the outer edge of the left-handed batter's box. In the first video, as he sets, Pearson's body obscures that area. In the second, he's wide of it. The Cubs moved Pearson about a foot across the rubber, toward first base. He's not throwing from a new arm slot, and the mechanical tweaks they've made are minor, but they changed where he throws from.

Let's explore what this means for Pearson's pitch mix, its utility, and his future. For these purposes, we'll stick to showing his four-seamer and slider, as I did above. Pearson has only thrown two sinkers as a Cub, and they were both in his first appearance for them. It would seem that the team doesn't want him to even worry about that pitch, which is a wise choice. They've also downshifted the usage of his curveball, although it's harder to say for sure that that change will have staying power in such a small sample. To be sure, the slider is his better breaking ball, so we can hone in on how it plays, especially off his four-seamer.

The first impact of this change in mound position we can easily identify is that Pearson is hitting the zone more with his fastball. That's an important and welcome change. He was only throwing the heater in the zone about 51% of the time with Toronto this year, but with the Cubs, it's just under 60%. That's a dramatic difference, and it explains why he's yet to walk a batter in a Cubs uniform.

Why does it work that way? Principally, when you change where a pitcher throws from, you force him to make a change to his release angle. We can now measure this angle, which is just the deviation from a straight forward line that the ball shows right out of the pitcher's hand. Is it going left or right? Up or down? Command comes from being able to consistently execute a release angle with a given pitch. Deception and swing-and-miss come from making those angles invisible or inscrutable to hitters. 

Here are Pearson's horizontal and vertical release angles on all his fastballs and sliders, with the Blue Jays and with the Cubs.

As you can see, there's a tighter distribution of release angles on the left, though time might spread them out. What's more notable is the less drastic average release angle, especially horizontally, and especially on the fastball. From his new place on the rubber, Pearson can throw the fastball fairly straight, letting his velocity, movement, and a very flat vertical approach angle keep the pitch not only close enough to the zone to induce a swing, but lively enough to avoid getting hit hard.

Speaking of that vertical approach angle, though, it's a key feature of Pearson's fastball, which would have relatively unimpressive raw movement without that factored in. We had better make sure he's not losing that ability to have the pitch ride and stay on a flat plane through the zone, because of this change. Here are his horizontal and vertical approach angles, which are the same as release angles but at the moment the ball is entering the zone, rather than at the moment the hurler cuts it loose.

Here, we see a huge difference--a bigger one, even, than that in release angle. Pearson the Cub doesn't have his slider wiggling sideways as much when it reaches the zone, but achieves a clearer separation in the approach angles of the fastball and the slider, vertically. In other words, while they're tough to distinguish out of the hand and there's not much lateral angle change to give them away, a hitter will get two very different pitches, vertically, as the ball reaches them.

A couple of outliers from his first two appearances even disguise the change Pearson has made since joining the Cubs. Here's the same approach angle chart, for his last three outings only.

His fastball still holds its plane into the zone--as well as ever, in fact. The slider is just a vicious, vertical snarl down off it, and he's still throwing these two offerings at about 98 and 88 miles per hour, respectively. Pearson hasn't yet piled up huge strikeout totals with this altered setup and series of looks, but there's good reason to hope that that's coming.

No relief pitching acquisition is guaranteed to be any kind of success. This pickup was very much a variation on last year's Jose Cuas trade, which came to nothing. Pearson has great raw velocity, a nasty slider, and some tantalizing secondary characteristics to his stuff, though. He's under team control two more seasons. And the Cubs clearly had an idea to make an immediate change, which could raise his ceiling for that remaining term of club control. It might never come to fruition, but Pearson has a real chance to emerge as a dominant reliever--not just a fine middle reliever, but a relief ace, like last year's version of Julian Merryweather. He'll be an important Cub to watch for the balance of this season.