Cooper Hjerpe is catching up for lost time in the Arizona Fall League. St. Louis’ first-round pick (22nd overall) in 2022, the 22-year-old southpaw was out of action from late May to early September due to an elbow issue and ended up tossing just 41 innings, but he was effective when healthy. Throwing from what my colleague Eric Longenhagen has called “a funky low-slot delivery,” Hjerpe fanned 51 batters, allowed 26 hits and posted a 3.51 ERA with High-A Peoria.

The Oregon State University product’s AFL stint with the Scottsdale Scorpions included a two-batter appearance in Sunday night’s Fall Stars game. Entering in the eighth inning, Hjerpe retired fellow former first-rounders Max Muncy and Jace Jung, the latter on a swinging strike. I caught up to the deceptive lefty after the game to ask about his pitch metrics and approach on the mound.

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David Laurila: We should start with a health update. What was the procedure you had this summer, and how is your elbow now?

Cooper Hjerpe: “I had what’s called arthroscopy surgery. A microscope went in there and took out bodies of cartilage. There were two pieces of cartilage at the front and the back of the elbow; they took them out and shaved what they came off of. It wasn’t like reconstruction surgery or anything like that. Everything is back to normal.”

Laurila: You throw from a low slot and approach angle, so I’m interested in what you can tell me about your pitch metrics.

Hjerpe: “The heater has changed a little bit. I don’t know if it’s the balls or what, but right now it has been like 10 vertical and 18 horizontal. The slider is anywhere from zero to negative-four vertical, with 14 to 16 HB [horizontal break]. The changeup is anywhere from positive-two to negative-three vertical, and negative-19 horizontal. The cutter, which I’m still working on, is 10 to 13 vert and around zero horizontal.”

Laurila: Did you know those metrics prior to coming to pro ball?

Hjerpe: “Yeah. I had a good gist of it in college. My agent works really closely with [the person] who did all of our analytics. He kind of gave me an inside scoop on hitters, what their hot spots were and all that stuff, so I had a pretty good idea of what their analytics were, as well as my own.”

Laurila: What do your consider to be your best pitch?

Hjerpe: “The heater. I have a lot of confidence in it. For offspeed, metrics-wise, it’s probably the slider… or, most effective, it’s the slider. I have more confidence in the changeup, though.”

Laurila: How would you define yourself as a pitcher? For instance, power guy, finesse guy, something else?

Hjerpe: “That’s a good question. I’ve never been asked that. I’d say that I’m deceptive. That would be the main thing. And the deception is effective when I’m in the zone.”

Laurila: What have hitters told you about your deception?

Hjerpe: “That it’s kind of an invisible fastball, an invisiball, and then the changeup kind of falls off the table. Same with the slider; it’s hard and goes in the opposite direction [of the slider] from the same plane. Mostly they say they can’t see the fastball sometimes, especially when it’s inside.”

Laurila: To a certain extent, hitters are going to be able to adapt to your deception the more they see you. Being a starter, how do you approach going after guys multiple times through the order?

Hjerpe: “I think it’s really just the generic ‘establish the heater inside and focus on establishing it on both parts of the plate.’ So first time through the order is establishing the fastball, not really showing them too much of the offspeed [outside of] certain hitters who have earned that, and then the next time through I’ll start incorporating more offspeed, sliders and changeups and all that.”

Laurila: Who do you comp to?

Hjerpe: “I’ve been comped to Chris Sale. I think Sale and I have the same numbers on certain things. And then Josh Hader’s and my vertical approach angle [are similar]. There is a lot of outlier stuff in between certain guys, and there are certain people I’m similar to, but I mostly just go out there and focus on what I’m good at.”

Laurila: Do you study comparable pitchers to see how their stuff works effectively?

Hjerpe: “Not too much. I mean, maybe Hader a little bit. Obviously, the heaters up. It works for him, so I started incorporating it, and it works for me.”

Laurila: Where are you velocity-wise?

Hjerpe: “The heater today was probably 88–91 [mph], and Hader’s is 97–98, so there is obviously some room for improvement there. But last year in the fall, I had an outing where I was 94–96 and topped out at 97, so I have stuff in the tank. It’s kind of frustrating to be 88–91, knowing that there is more in the tank. That said, everyone can gain velo.”

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