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Trouble with the slurve: Gunnar Henderson’s early struggles and future adjustments

The problem: breaking balls in and around the hands. The solution: just being patient, as Henderson will eventually figure it out.

MLB: Detroit Tigers at Baltimore Orioles Tommy Gilligan-USA TODAY Sports

I don’t know why many ballplayers burst onto the scene as rookies, announce themselves with a bang, and go through a protracted slump right after. Pitchers figure out you can hit a fastball and adjust, I guess. Ryan Mountcastle went through it, punishing the ball in 35 games as a rookie in 2020 (with a .333 average and .878 OPS) before faltering early the next April, slashing just .198/.229/.286 that month. He burst out of it, but it was still a trying stretch.

The latest guy to go through this is the preternaturally talented Gunnar Henderson. Drafted in 2019 as a 19-year-old out of John T. Morgan Academy in Selma, Alabama, Henderson absolutely blazed through the minors. The youngest guy at each rung he climbed, Gunnar had an impressive .866 OPS in 246 games between Low-A Delmarva and Triple-A Norfolk before the call-up came for him on August 31, 2022.

Henderson, similar to Mountcastle, had an impressive 34-game stint with the Orioles last fall, managing a .259/.348/.440, a .788 OPS, and a 124 OPS+. The power and the patience showed through clearly. Combine that with defensive range, sure hands, and a powerful arm from the left side of the diamond and suddenly, the question wasn’t whether the O’s No. 1 prospect would stick in the big leagues, but only where the Orioles would play him.

We’re only 23 games into 2023, but for the young buck it’s been a rude awakening. Gunnar is slashing a measly .203/.363/.344. He’s struck out 26 times in 80 plate appearances, a bloated 32.5%. Whereas last season almost 54% of Henderson’s batted balls were hard hit (95 mph or more) this year only 42% are.

As 4 Non Blondes once posed the question [dated reference alert]: what’s going on?

Here’s what’s not: the pitch mix Henderson is seeing, which has stayed almost exactly the same over the two months he’s been in the big leagues, September 2022 and April 2023. Throughout, Henderson has faced a consistent diet of fastballs (53%) and hit them consistently, averaging an impressive .322 against heaters in 2022 and .300 in 2023. (His average exit velocity off of fastballs is actually up by 2.5 mph this year, so the contact has been good.)

What has changed, however, is location. Last season, Gunnar saw many more outside pitches than inside ones, especially low in the zone (115:85). This year, the ratio of outside-to-inside is largely even (66:62). What this means: opposing teams seem to be cuing into a weakness down around the hands.

Gunnar Pitch Map 2022
Gunnar Pitch Map 2023

In that same part of the zone, Henderson’s expected average is a stunning .009 (!), his whiff percentage is 80% and his average launch angle is -11. Translation: in the low-and-inside quarter of the zone, Gunnar Henderson is swinging over pitches (particularly breaking pitches) or making weak contact on them.

One idea about what could be causing this: Henderson’s swing. His power numbers are not down; in fact, his launch angle is up by 10% and his groundball percentage is down by 15%, despite his diminished quality of contact (e.g. his hard hit % is down 11% this year). Henderson was bad against breaking balls last season (an .184 expected average), but this year the heater-breaking ball gap is even worse: he’s faced 109 of these pitches and is actually batting .053 against them (.132 xBA). More troublingly, Gunnar’s whiff rate on breaking pitches has ballooned, from 33.9% last year to 50.0% now.

I think it’s possible the rookie has been given an assignment to focus on his power by developing something of an uppercut, and that this is hurting his performance against low-and-inside pitches. This also seems likely because it’s not like he’s been swinging wildly at everything: Henderson’s overall walk rate is up by 6% and his swing percentage is down by about that much, too. He’s being choosy; he’s just not making good contact on the low pitch.

All this said, there is abundant room for optimism: Henderson is likely to make adjustments and correct this problem. One reason to think so: he’s always done this. In early 2022, MLB Pipeline wrote, “Henderson has always been young for his level and the Orioles have been pleased with how he’s responded with the challenges each promotion presented.” Over the seasons, the report noted, the lefty has continually cut down on his swing-and-miss rate and made “strides on pitch selection, chasing out of the zone and maintaining his emotions in the box as he’s moved up the ladder.”

We’re seeing a similar issue now, and we should believe Henderson will continue to show his adaptability—not just because of his reputation, but also because of his age and his recent trends. The 21-year-old Gunnar Henderson is younger than all but two current MLB players, the Cardinals’ Jordan Walker and the Rockies’ Ezequiel Tovar. And over the last two weeks, he’s slashing .273/.400/.424 and over the last week, that’s .313/.353/.563.

It’s been a slow start to 2023 for Gunnar Henderson, but this top prospect and ROY candidate has lot of room to grow. Stay tuned as he does.