Everything You Need To Know About Zac Gallen

Nick Pollack's Going Deep article pledge #5 featuring Zac Gallen.

Editor’s Note: With MLB owners forcing us to miss games in 2022, I have pledged to write a Going Deep article every day until the lockout is lifted. Please consider supporting Pitcher List with a PL+ subscription to help us survive through these difficult months.


It was a late Friday night in September 2019. I waited patiently in my bedroom over Skype, staring at the cement wall of a non-descript room inside the Arizona Diamondbacks clubhouse until Zac Gallen sat down in front of me with a welcome smile.

I hit record and we had a fantastic chat for the next thirty minutes, discussing his rapid acceleration in the minor leagues, the development of his repertoire, his mentality during starts, and so much more.

It was incredible. I’ve been a “Gallen Gal” ever since his debut as a Marlin, and talking shop for thirty minutes had me ecstatic. There was one problem.

I had only recorded my audio.

I listened back to the recording after and only heard my voice as Gallen’s was mysteriously missing from the track. A terrible one-sided conversation with interwoven silence that held zero importance.

Those next moments were a complicated mixture of agony and panic, and filled with energy granted by Gallen’s insights, I wrote down everything I could remember, using my recorded questions to help trigger my memory.

Remember, that was September 2019. It’s 29 months later and this draft has survived in my WordPress backend, longing for its release into the public eye.

Today is the day, old friend.

This article will be a little different than the standard affair. I’ll be inter-weaving GIFs and analysis with Gallen’s thoughts, though you will find few direct quotes due to my technological horror. We’ll get through this together.


The Development Of Zac Gallen


A quick rundown of Gallen’s history: Drafted by the Cardinals, sent to Miami with Sandy Alcantara (and two others) for Marcell Ozuna, debuted, traded to Arizona for Jazz Chisholm, fractured his right forearm before the start of the 2021 season, returned, strained his hamstring, then completed the season with the club.

We chatted a bit about these transitions and his development. Having pitched with three different organizations, Gallen had some great insight into the differences in developmental approach, albeit this was at the end of 2019.

After drafting Gallen, the Cardinals were hands-off. They wanted him to get comfortable in their system without startling him with tweaks and analytics bombardment. Makes sense … and I wonder if that’s the standard approach for young arms in the system. Something I’ll continue to ask moving forward.

The Marlins were a bit different. On one hand, Gallen expressed enthusiasm for the growth of the Miami analytics team when he was there, indicating they showed promise in future years as they had invigorated interest in using metrics to guide their starters.

We can also thank the Marlins for moving Gallen from the first base side of the rubber to third base, emphasizing Gallen’s closed stride toward home. They also shifted his arm angle to be more over the top, and he quickly got more comfortable with the new release. We saw a massive jump in performance during his Triple-A stint in 2019, and it may have been a product of these tweaks.

After being traded the Diamondbacks, Gallen had plenty to gush about. Dan Haren was brought into the organization in late 2016 and acts as the team’s pitching specialist, helping Gallen develop further. He felt the team’s developmental process was “tailored to you”—a seemingly great fit for the young right-hander.


Can We Please Talk About The Pitches?


You’ve been bombarded with walls of text thus far and it’s time you had some respite. What makes Gallen so appealing in my eye is the depth of his repertoire: a four-seamer that gets called strikes constantly + a trio of secondaries that each have their moments in the sun. And it’s time I outlined them proper as they weren’t quite what we wanted them to be in 2021.

The heater is often the rock of an arsenal and Gallen’s is no exception. Let’s start there.




You want a GIF? Here’s a GIF:


Growing up, Gallen idolized Mike Leake and adapted a two-seamer/changeup approach initially. He eventually scrapped the horizontal heater for the four-seamer and he’s better off for it. When you have three stellar secondaries, it’s nice to have a rock in your fastball that gets the job done:

Zac Gallen’s Four-Seamer

Interesting shifts here. Gallen has been lowering his heater consistently across the last three seasons, which may be a focused approach change, though I wonder if it’s a product of that zone% and strike% rising.

You see, the biggest issue for Gallen in 2021 was his inability to get a proper feel for his three secondaries, forcing him to use his heater more often (54% usage!) to get strikes in the zone. It then led to the pitch getting clobbered more than usual.

As for the location change, notice the increase in Behind%, meaning Gallen tossed a higher rate of his heaters when behind in counts than in previous years. When in hitter’s counts, pitchers generally refrain from elevating as it’s a larger risk-reward approach than sitting low—high pitches that are put in play result in more flyballs (thus homers) than low pitches.

If Gallen is able to get more strikes with his secondaries this season, expect a lot of these numbers to fall closer to those from 2019 and 2020 on his heater.




Of his secondaries, Gallen had the most success when his curveball was in a groove. However, he struggled to find it relative to previous seasons, showing a near 8 point drop in strike rate as he failed to get called strikes as often as he used to.

You can blame its worse locations for the lack of strikes. Take a look at their strikezone plots from 2020 vs. 2021:

In 2020, the hook did a wonderful job teasing batters as it flirted with the bottom of the zone. Its questionable final location inflated its O-Swing to a massive 46% rate, which fell to a great-but-not-elite 41% in clip in 2021.

Here’s to hoping the pitch can come back into form and we can see its usage rate bump up closer to 20% in the season ahead. When it works, it’s a staple in his arsenal and will protect his fastball from destruction.




This was the pitch for Gallen and suddenly in 2021, it wasn’t. Take a look at how the pitch fell off the table (analytically):

Zac Gallen’s Changeup

I’m honestly at a loss. Gallen even gained an inch of drop on the pitch, dropped its exit velocities on flyballs, held below average barrel rates, etc. Yet the pitch allowed plenty more contact, induced fewer swings outside the zone, and reduced his strike rate to a poor 58% rate. It makes no sense and please reach out if you have some answers here.

It just seemed more hittable for whatever reason. It’s possible he telegraphed the pitch through sequencing or tipping more than ever, or maybe his injury caused him to lose the feel he once had.

I’m willing to wager that the pitch will come back for him this year given the lack of startling explanation for its dip in 2021.


Cutter And/Or Slider


Here’s the thing. I talked to Gallen in 2019 and had this awesome talk about what this pitch was. Essentially, it’s a slider but he mentally needed to think it was a cutter to force himself to stay behind the ball longer on release, preventing him from wrapping around the ball.

It’s been over two years since that lovely conversation, though, and it looks as though in 2020 he began throwing two distinct pitches.

Here’s the harder cutter at 91 mph:


And here’s the loopier slider at 86 mph:


And neither of them got strikes consistently for Gallen in 2020: cutter sitting at 59% and the slider at an abysmal 53%. Hard cutters are generally utilized as zone pitches or temptations off the inside corner to opposite-handed batters, resulting in exceptional strike rates. A sub 60% rate is startling to say the least and is clearly something Gallen is still working on. H*ck, Gallen almost evenly split its usage against right-handers and left-handers, though he heavily focuses the pitch arm-side, regardless of the batter.

The slider has been a strong pitch for Gallen in the past, though. We’ve consistently seen SwStr rates in the upper teens result from it, and while Gallen discussed how his feel for the pitch shifts start-to-start, it has plenty of promise to propel strikeouts.


Approaching A Start


may have gone a little loose on the repertoire stuff because I was stoked to talk more about Gallen’s approach. During his MLB debut in St. Louis, I was impressed with his confidence in his secondaries and it even made me make a quick video breaking down a specific at-bat against Paul Goldschmidt:


The best takeaway from the at-bat was the 3-2 offering, a filthy changeup under the zone that Goldschmidt couldn’t resist. I asked Gallen about this specific pitch and he recalled Goldschmidt had launched a heater just left of the foul pole down the line earlier in the at-bat. Despite no outs and Marcell Ozuna coming up after, Gallen felt confident he could deal with Ozuna (in Gallen’s MLB debut, no less!) and elected to gamble with the changeup.

You gotta love it.

Gallen’s faith in his secondaries extends into more than just situations like these. Our conversation led to pitching philosophies, including when to showcase your full arsenal to the opposing lineup—do you save your curveball for the fourth or show it early?—and I can distinctly recall Gallen’s response:

“Think like a closer in the first inning.”

He went on to explain the importance of getting out of the first as quickly as possible and even emphasized his love for getting into batters’ heads. Gallen’s philosophy was to display all four of his pitches early, creating mind-games for future at-bats, knowing he’s capable of throwing any pitch in any count. I’ll be honest with y’all, I absolutely love this.

Gallen even tossed fewer than 30% fastballs in his debut, reinforcing the notion of his arsenal flexibility. He outlined how he was following what his battery-mate was putting down, and if other pitches were working, he’ll go with the flow of the game. When you have a full four-pitch (five-pitch?) mix, it creates more paths for game success, and while he’ll listen to analytics in-between starts, the game itself dictates what he throws next, moreso than what’s inside a spreadsheet.

Finally, we discussed attacking batters from either a north-south or east-west approach. Originally he was east-west (remember, Mike Leake!), but he shifted to north-south as he leaned into the four-seamer, allowing his off-speed pitches to flourish down in the zone.


2022 Outlook


With all of that in mind, I do want to remind everyone that the insight from Gallen is still dated—this was a discussion in September 2019, and it’s been years since. That said, a lot of his philosophies ring true today, and I’m excited to see how they play out in a potentially injury-free season ahead.

So what should we expect that season to look like? It hinges heavily on the success of his off-speed pitches finding more strikes. If his changeup can overwhelm batters once again, he’ll have to rely less on his four-seamer and keep batters guessing. I’m curious how the slider/cutter develops further this season as well, and whether he can turn back into the more north-south arm of previous seasons.

As long as there’s consistent health, I’d imagine Gallen can get back into the groove of 2019 and 2020 again. The Diamondbacks will let him pitch every fifth day, and he’ll maintain a high 90+ pitches per game once again, allowing him to find the sixth constantly. I’m excited to watch the rebound unfold.


Featured image by Justin Paradis (@JustParaDesigns on Twitter)

Nick Pollack

Founder of Pitcher List. Creator of CSW, The List, and SP Roundup. Worked with MSG, FanGraphs, CBS Sports, and Washington Post. Former college pitcher, travel coach, pitching coach, and Brandeis alum. Wants every pitcher to be dope.

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