When you watch a left-handed pitcher who throws in the low-to-mid-90s with a changeup and a slider you probably assume he’s a pitchability type of guy. Then you go and look at his metrics, and his walk rate, and you’re likely to come away with the same conclusion. This, however, is not what DJ Herz is. No, Herz pitches like a high-leverage reliever with unflinching confidence in his stuff and its ability to get the job done. It feels a little strange to call someone with his arsenal a “power pitcher”, but by his results, he fits the description.
The Stuff
Herz’s entire profile as a pitcher is driven by his excellent fastball. For once, the pitch data cannot be trusted here. What it depicts as an utterly generic and uninteresting fastball is closer to an invisiball that hitters can’t pick up at all. Herz pitches with a deceptive crossfire delivery that allows him to conceal the ball behind his head until just before he releases it. This is how he’s running such ridiculously high whiff and swinging strike rates. Imagine what happens when he starts to elevate it more. He’s getting swings and misses at an elite clip without even throwing his fastball above the zone that often. He has an uncanny knack for spotting the pitch on the low glove side corner like a Maddux sinker, which can work with how much arm-side run he gets but also probably isn’t the best way he could be using it.
Think about it this way: Herz is using his fastball in excess, which allows hitters to sit on it, and they are still incapable of doing anything with it most of the time. Fastballs in the 96th percentile of usage usually aren’t in the 99th percentile for SwStr%. That is the dream foundation for a starting pitcher, an A fastball that can be used in any situation with confidence. Herz’s is a bit unorthodox, and unlike what you would normally think of as an ace’s fastball, but who are we to say it’s not when it performs like one? It will likely have some issues with barrels and homers like most pitchers with high-whiff fastballs do, but that comes with the territory and is an acceptable sacrifice. Surprisingly, it hasn’t run into much trouble in that way yet, but there will likely be days that it does.
Herz’s changeup is the pitch that the scouting reports on him before getting to MLB said was his best weapon. It’s a strange offering with a high spin rate and no SSW but with high spin efficiency. It seems to be a sort of proto-airbender. However you want to classify it, this pitch has good vertical and velocity separation from the fastball, and its spin likely makes it more deceptive. His command of the pitch is still a work in progress, but it has the potential to be a big part of his arsenal in the future.
Herz has a solid bullet slider with power and depth that should carve up right-handed hitters. The problem is he has no idea where it’s going. He’s thrown about as many of them down the middle as he has in good spots. This is probably the biggest flaw he has to fix if he wants to reach his potential. It’s an excellent pitch in the pitching lab but he has to get it down and out of hitters’ wheelhouses. It’s been hit very hard due to where he’s been throwing it.
His curveball shows some signs of potential as a slightly slow gyro curve. We’ve seen the combination of two gyro breakers work for other pitchers such as Eury Pérez. I could see similar pitch success for Herz if he could locate this curveball, but its location chart to this point has been way too scattershot to date.
The Potential
He’s putting together a respectable rookie season on the back of a single pitch. His other stuff shows signs of being good but it isn’t what’s carrying the load right now. The fastball is getting him to near league average on its own. That is as good of a base as you could ask for as a pitcher. It’s why I think he’s potentially the most unassuming top prospect right now. Watching him you don’t immediately think “future ace”, but looking for the individual pieces you’d find that they’re all present or have the potential to be. Even if all of his other offerings are in the developmental stage, a fastball that plays the way his does makes him someone you can never fully write off.
It cannot be stressed enough that a fastball thrown as often as Herz is throwing his should not be working this well. It may regress if he continues to do so but he’s found an astonishing amount of success with it so far. But imagine what happens when the other pitches take a step forward. When he can take some pressure off of the fastball and use the other pitches to their full effect. Hitters would have to make a choice to either keep sitting on the fastball and let the secondaries beat them or to expand their approach and risk looking silly when the fastball goes above their bats. With how the fastball has worked to date, he likely only needs one to improve to be a volatile but effective big leaguer. Think what would happen if he got two of them working.
It’s important to remember that Herz is just 23 years old, and has been climbing the ranks with good results despite a walk problem. He’s cleaned up the walks at this level so far, but his command is still questionable at best. With that in mind, even the slightest of improvements to it could send him skyrocketing up the ranks as his key drawback is throwing too many pitches in bad locations.
He’s getting strikeouts, he’s limiting walks, it’s just the contact that’s killing him. I don’t think he has much need for a sinker given how much managers like to play platoon matchups against him. His splits will likely even out eventually, he’s struggled with lefties this year, probably a mix of small samples and not having anything with significant horizontal movement outside of the changeup. A sinker would help with them but that would be a highly situational pitch, I’d rather he continue to work on what he has than start something new.
The Outlook
All of this comes down to improving his pitch execution and command. While the stuff doesn’t look dominant in the traditional sense, it has the potential to be excellent despite its oddness. Cleaning up his walk rate upon getting to the majors is a promising sign that he could continue to develop his command. I don’t think a change to make his mechanics simpler would be a good idea in his case as his deceptive delivery is a big part of what makes his stuff so effective. If he can get the same effect while only pitching out of the stretch I’d advocate for that. It’s a small sample but his numbers with runners on vs. off are pretty close with the advantage going to runners on, surprisingly. Could be worth looking into if it would improve his ability to repeat his delivery and locate his pitches.
That’s speculation though, what we know for sure about Herz is that he has excellent stuff and iffy command, which makes him like most other top pitching prospects, it just looks a little different. Do not let his underwhelming eye test and stuff metrics fool you, this is a nasty pitcher. You do not strike out 29.0% of hitters as a starter by accident. Furthermore, doing it with one pitch that you trust enough to throw 56.6% of the time is all the more remarkable. All that’s left is to lock in with his other pitches. It’s a tall order for most pitchers, but I’ll be watching him patiently. What he could be is too exciting to not wait for it.