Zac Gallen Must Focus on Improving Fastball Command

Arizona Diamondbacks' star pitcher Zac Gallen is entering the most important year of his career, as he will reach free agency after this season. Gallen has a pretty strong track record from 2022-2024, going 43-19 with a 3.20 ERA and 3.22 FIP across 90 starts. One more solid season would be enough for him to secure more than $150 million in the open market.

However, despite the strong track record in the past, there is a troubling trend involving the Diamondbacks' ace that needs to be corrected as quickly as possible. That trend is a slight decline in overall fastball command. Gallen needs to command the fastball well, as establishing that pitch allows him to open up the entire arsenal and keep opposing hitters guessing.

The inability to command the pitch was a problem in his Opening Day start, as he landed just 15 of the 43 fastballs (34.9%) in the strike zone. Most of the misses came in the second inning, as he walked two batters and threw 11 straight balls in what was a 29-pitch inning. He was able to correct it in the next two innings, but the damage was done, and he had a short start.

That continued a negative trend that began at the start of the 2024 season. Gallen was very aggressive with his fastball in 2023, landing over 58% of them in the zone. That rate dropped to 53% in the first half of 2024, then to 49% in the second half.

Adding a bit of context, the league average of fastballs in the strike zone is around 54-55% in a given year. A difference of 5-6% compared to the league average seems like a lot at first glance, but it's only two to three pitches per game that have to improve.

Zac Gallen Zone% Since 2022 by Season Halves show a drop from high 50's to low 50's over the last year — Zac Gallen Zone% Since 2022 by Season Halves | Michael McDermott

Command isn't just the ability to throw strikes, but also locating on and around the edges of the strike zone. The appropriate attack zone for these pitches is the "Shadow Zone" on Statcast. In a typical season, the league average of fastballs in the shadow zone sits at 44-45%, but Gallen shows an exceptional ability to locate in those spots.

Since the first half of the 2022 season, he's located in that zone around 45-48%, well above the league average. The lone exception came in the second half of 2023 when he was much more aggressive in the zone with his fastball, with 32% in the heart and 44% in the shadow zone.

Zac Gallen Heart and Shadow% on 4-Seam Fastballs | Michael McDermott

Gallen's ability to land his fastball in the shadow zone has been a successful approach earlier in his career. Looking at the wOBA against his four-seamer, Gallen yielded marks of .256 and .290 in 2023, but it significantly worsened to .366 in 2024 as his percentage of fastballs in the strike zone declined.

The decline in results could be a combination of two things: batters being more aggressive against in-zone fastballs and falling behind counts with fewer competitive pitches.

In his next start against the New York Yankees, his ability to command the fastball will be key to righting the ship. New York is coming off a dominant series sweep of the Milwaukee Brewers, launching 15 home runs over the weekend, and any location mistakes could spell doom.

Zac Gallen must locate his fastball on the edges of the zone, especially early in the count, to put the Yankees' hitters on the back foot and open up his entire arsenal. If he can do that, he'll keep the Arizona Diamondbacks in the game and give their top rated offense a chance to keep pace with New York's.