Let’s Fix an Unbroken Zach Eflin

Zach Eflin broke out in 2020, but there's room for growth.

A couple of years ago, I wrote that there was something of a precedent for Zach Eflin in Zack Wheeler. Both have historically been trendy candidates to take that next step, but neither has been overly compelling to date. Sure, Wheeler has been plenty productive—and he got paid like it—but until 2020, Eflin hadn’t really broken out. He has a chance to hit a second wind, too.

This wasn’t always the case. In 2019, it became publically known that Eflin was resisting coaching suggestions. After starting to lean on an approach that emphasized elevated fastballs in 2018, Eflin came out with the same formula in 2019, before ultimately reverting back to his sinker. Tim Jackson wrote about this in August! Not long ago, I might have said going sinker-heavy was a poor decision on Eflin’s part. Now? I think he was right all along, but with a caveat of sorts.

It’s hard to say with certainty what exactly it is that precipitated Eflin’s gains. That’s probably because there are several factors at play. Perhaps part of it is pitch tunneling and deception, given that he’s tightened up his release point. Another answer is that he’s getting more extension on his pitches. He’s always been plus in this way—he ranked in the 74th and 85th percentile in pitch extension—but now, he’s jumped into the 95th percentile. As far as I see it, these are both answers.

Months ago, Meghan Montemurro of The Athletic wrote an article detailing Eflin’s confidence in his curveball. Eflin talks about using a grip it and rip it mindset with his curveball, treating it like a fastball mentally, to better throw it with conviction. It worked! Eflin moved from 61st and 67th percentiles in curveball extension in 2018 and 2019, respectively, to the 95th percentile in 2020. Perhaps more importantly, it led to a more repeatable release point for him.

Eflin’s curveball release point, 2019 versus 2020:

As is intuitive, release point repeatability leads to increased pitch execution. Eflin’s curveball characteristics themselves didn’t change all that much — it was mostly that his curveballs were more consistent movement-wise. This doubled consistency in location and movement led to (a) more swinging strikes in the zone, (b) more swinging strikes out of the zone, and (c) fewer misses. The former two are probably due to the latter, but perhaps most importantly, Eflin’s increased confidence in his curveball allowed him to more than double its usage. After all, if Eflin doesn’t have confidence in his curveball, he’s simply not going to throw it.

Perhaps you know where I’m going with this, because I’m hardly alone in thinking this. I think Eflin should throw his curveball more—a lot more—and I think there’s a pitcher he could (and should!) model himself after. This time, it’s not Wheeler. Enter Charlie Morton.

Eflin Versus Morton, Since 2018

Now, obviously, Eflin isn’t Morton as-is. He’s going to need to make some pretty substantive changes to get into Morton territory, but when it comes to their pitch repertoire and movement, Eflin feels an awful lot like Morton-lite. His curveball doesn’t quite get the sweep of Morton’s, but it gets equal drop, and they throw similar fastballs. (Although Morton’s is generally harder and better.)

already thought Eflin should increase his curveball usage by a lot, but now I think he could stand to match Morton’s usage. Here’s what their repertoires looked like in 2020:

Eflin and Morton, 2020 by Repertoire

Morton essentially throws a four-seamer, curveball, and sinker. Eflin throws a sinker half of the time, and then other stuff the other half of the time. His sinker is legitimately a great pitch, so he shouldn’t lower its usage too much, but his curveball should be thrown more. The slider and changeup should be thrown less. So, this is what I’m proposing:

Eflin, Proposed Pitch Mix

What I’ve come up with is about as realistic of a pitch mix that I can envision Eflin moving towards. He’ll probably continue to throw his slider too much, and he might not feel this confident in his curveball, but it’s plenty reasonable on the whole.

Now, this is overly simplistic, but if we take Eflin’s pitch mix and plug his 2020 CSW into it, it can give us a little bit of an idea of what his numbers could look like in 2021, given my proposed change. I plugged the numbers into a spreadsheet, and here’s what it spat out:

2020 CSW: 30.1%

2021 CSW: 32.0%

With a pitch mix change, Eflin could have theoretically vaulted himself from the 68th percentile in CSW to the 84th percentile. Of course, a change in pitch mix has several ripple effects, and so it’s much more complex than plugging some numbers into a spreadsheet, but I don’t think it’s disingenuous to say that he could take this leap in CSW, and that’s nothing to say of the gains he would make by moving towards a curveball that not only doesn’t get hit hard, but it also means his fastballs get hit hard less too.

Piecing together some pitches from a few at-bats facing Yadiel Hernández, here’s a taste of what Eflin could look like in 2021.

First, a sinker for a called strike:


Eflin could then follow it with a four-seam fastball. This time, a little higher:


And then perhaps go for the kill with a curveball:


Of course, they’re all pitches to the same batter in the same game, but they’re also from different at-bats. What I’m trying to emphasize is that Eflin could stand to use these three pitches in enough ways that they can play off one another, especially as he uses each offering in multiple ways. He can paint sinkers on the corners, but he can also run it off of the plate, or front or back door it for called strikes. He can flip his curveball into the zone for strikes, but he can also use it as a chase pitch to put hitters away. He can mix in elevated fastballs. His fastball and sinker play off one another as-is, so Eflin has quite the toolbelt at his disposal. And that’s nothing to say of his changeup and slider, which exist, I guess.

Eflin is fine as he is. It’s just that, if he wants to be a better pitcher, there’s a pretty easy path to doing so. Not long ago, his curveball was an afterthought. Now it’s providing him the chase pitch that’s he’s sorely lacked for the entirety of his young career. It’s time we consider Zach Eflin broken out, if we don’t already. And he might be gearing up for a second wind of sorts.

Photo by Gavin Baker/Icon Sportswire | Adapted by Doug Carlin (@Bdougals on Twitter)

Michael Ajeto

Michael writes about the Mariners at Lookout Landing, as well as here at Pitcher List. You can follow Michael on Twitter @dysthymikey, or you can not.

2 responses to “Let’s Fix an Unbroken Zach Eflin”

  1. Perfect Game says:

    Nice write up.

    BTW, when is Nick putting out The List? We’re coming up on spring training.

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