Adjustments

Full Tilt

There’s an at bat from Tuesday’s 1-0 win over the Diamondbacks that’s worth putting under a microscope. It’s an obvious choice, but it was remarkable even before its conclusion.

First the preamble. For the second night in a row the Diamondbacks starter had significantly better stuff than their previous season averages. Merrill Kelly saw noticeable upticks in velocity of every pitch Tuesday:

And like Zac Gallen the night before it wasn’t just velocity that was better. Look at the difference in Kelly’s pitch shapes (from TJ Stats):

Every single pitch type saw an increase in horizontal break, including a giant 3.5 inch difference in the curveball break. The induced vertical break (iVB) was just as notable with the 4-seam fastball and cutter playing up with a more positive iVB, and the changeup, sinker, and curveball having a more negative iVB. Just the changes you would hope for to improve the effectiveness of each pitch. And as you’d expect the difference in stuff+ and pitch grades is dramatic:

It’s hard to say what’s behind this happening in back-to-back nights. This could just be two pitchers recognizing that these games mean more than usual, reaching back for a bit more juice. There could be more than one cause, perhaps the previous explanation causing the velocity increase while the denser seaside air of Petco explains the increased break. Hard to say. But regardless, it made for an exceptionally difficult hitting environment. Kelly was masterful. And the Padres were scoreless entering the bottom of the 7th.

Luis Arraez led off the inning. When Arraez is up with the bases empty the expected value of his contributions—frequent base hits with a preponderance of singles—is at its lowest with no chance for extra base advancements from runners on. This is part of why he’s miscast as a leadoff hitter, especially in a lineup that shows no on-base ability from the bottom of the order. He was moved out of the leadoff spot after only five games on his recent stint atop the lineup. But Tuesday the game flow brought him up to lead the heart of the Padres order through perhaps its last chance to get to the dazzling Kelly who had mowed down the Padres order the first two times through. And it’s fair to wonder if he made a conscious choice to approach this at bat differently.

Intent

You can never truly know what’s in a player’s mind. Intent isn’t in the box score. All you have are crude stochastic tools for inferring intent. Reading the game situation and body language is as close as you’ll get. But this just had the look and feel of an intentional approach.

Here’s the first pitch of the at bat, notice Arraez shake his head after:

It’s typical for a pitcher to show a hitter a different pitch mix the third time through. Kelly had shown Arraez only fastballs the first two at bats¹. This was the first curveball Arraez had seen. And it was not the pitch he was looking for.

Nor was it the only pitch he hadn’t seen yet. This came on Kelly’s second offering, the first changeup of the evening:

Arraez clearly had no intention of swinging—he fidgeted in the box, never getting into a functional hitting posture. When Kelly didn’t get the call on the edge of the plate the count ran to 2-0. The quintessential hitter’s count. And the final pitch of the at bat is the most interesting:

A 2-0 four-seam fastball itself isn’t a surprising or interesting result. What’s interesting is to juxtapose Merill Kelly and Luis Arraez’ execution. This fastball was the slowest four-seamer Kelly threw all night, with the lowest iVB:

Arraez took the opposite tack. Here is the typical swing path of Arraez in 2025:

He averages a bat speed of 63.2 MPH, with a line drive oriented 6 degree attack angle with an opposite field attack direction. It looks like this:

But with the count 2-0, and a fastball he’d seen multiple times already likely to be thrown in the zone, here are the kinetics of the swing he took on the flaccid offering from Kelly:

A 67 MPH bat speed is still well below league average, but is full tilt for Arraez. And the changes in the swing path are optimized for launch. That was an A-swing. And look how immediately Arraez knew this was gone:

This doesn’t look like a slap hitter who happened to run into one. There’s just no uncertainty at all in his reaction. This looks like a hitter who knew on contact that he’d executed his planned approach.

Adjustments

Maybe it’s just a coincidence that Kelly’s worst fastball of the night was thrown in a perfect hitters count when you’d expect maximum effort. Or maybe Kelly had a diminished sense of danger after seeing very unserious body language from a supposed singles merchant. Maybe that clownshoes statue take was Arraez playing with his food. Probably not, but it’s fun to consider.

But even if Arraez wasn’t playing rope-a-dope, there’s good reason to think that his swing decision was intentional. Once the count became 2-0 he was up there trying to launch. And it’s this that deserves a spotlight. Because for most of the past year Arraez has not been making the same quality of contact he did for the first 2500 at bats of his career. For whatever reason² too many of his line drives have been replaced by popups and lazy fly balls… And he hasn’t seemed to make adjustments.

Working counts and ambushing pitches are tricks that he simply hasn’t had to rely on in years past when he was able to find consistent success expanding the zone and still sprinkling line drives across the field. His path to success was unique. But there’s no shame in adopting the common tools of the trade. Hitters use them for a reason.

1. First at bat:

Second at bat:

2. Could just be coincidence: