Joey Wentz had shown flashes of brilliance in 2022, despite starting only 18 games between Toledo and Detroit due to injury. With the known injuries, we were hoping he would hold one of the rotation spots down and pitch fairly well. Nine starts in and we have seen Wentz accumulate a 5.79 FIP and 2.09 HR/9, which couldn’t be further from what we wanted to see. So what is going on?

Data

There seems to have been some mechanics changes in Wentz between 2022 and 2023. He’s getting more extension:
4-Seam Fastball: 6.2 in 2022, 6.4 in 2023 (+0.2 feet)
Changeup: 6.4 in 2022, 6.6 in 2023 (+0.2 feet)
Curveball: 6.2 in 2022, 6.4 in 2023 (+0.2 feet)
Cutter: 6.2 in 2022, 6.5 in 2023 (+0.3 feet)

And more velocity:
4-Seam Fastball: 92.4 in 2022, 93.7 in 2023 (+1.3 MPH)
Changeup: 84.1 in 2022, 86.3 in 2023 (+2.2 MPH)
Curveball: 75.4 in 2022, 77.7 in 2023 (+2.3 MPH)
Cutter: 83.4 in 2022, 86.1 in 2023 (+2.7 MPH)

He’s even seen bigger spin rates on a couple of his pitches:
Curveball: 2291 in 2022, 2530 in 2023 (+239 RPM)
Cutter: 2295 in 2022, 2410 in 2023 (+115 RPM)

But here’s the most troubling part. Let’s look at his run value for each of his pitches:
4-Seam Fastball: -1 in 2022, 8 in 2023 (+9 runs allowed)
Changeup: 2 in 2022, 0 in 2023 (-2 runs allowed)
Curveball: -1 in 2022, 1 in 2023 (+2 runs allowed)
Cutter: -2 in 2022, -1 in 2023 (+1 runs allowed)

Fastball

Fastball has seen nine additional runs of value added to it from 2022 to 2023. To make it worse, it’s a pitch that has been thrown almost an identical amount of times between last year (306 times) and this (304 times). Of the 9 home runs Wentz has given up this year, 5 have been on the fastball. By comparison, neither of the 2 home runs he gave up last year were on the fastball. So what could be going on with his fastball? Let’s take a look.

Here’s his release point for fastballs in 2022 (blue) and 2023 (orange):

And here’s where I include the additional extension.

It’s clear there is a difference. A fairly large difference at that. His arm seems to be outward more, which might be the reason he’s able to release the fall later in his delivery. As I noted above he gained 1.3 MPH, he also gained in perceived velocity thanks to his additional extension. Now I would like to look at the location for his pitches:

As we can see, 2023 his fastball is seeing a lot more of the heart of the plate and much less outside of the strike zone. Using the indicators on the right of each plot, we can see not only that there is more coverage, but also the frequency has increased. Which would certainly explain the explosions in home runs allowed. Not only that — we can see that he’s wasting a lot of these pitches compared to last year. Anything outside of the big, blue square is in the Waste zone. Especially up we see him using that.

Final thoughts

Is this change the cause of his fastball issues? To me — yes. I think there is a correlation here between the two. And I think it’s something that can be fixed; whether reverting back to last year or another small mechanic change. Regardless, hopefully it will get figured out and we will get the Joey Wentz of 2022 back.