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2021 Arizona Diamondbacks Player Reviews, #9: Zac Gallen

Gallen struggled with injuries for the first half of the season, but had a strong finish to the season.

MLB: Los Angeles Dodgers at Arizona Diamondbacks Allan Henry-USA TODAY Sports
  • Rating: 5.78
  • Age: Turned 26 on August 3rd
  • 2021 Stats: 23 GS, 4-10, 4.30 ERA, 121 13 IP, 1.294 WHIP, 139 K, 49 BB, 2.1 bWAR
  • 2021 Earnings: $750,000
  • 2022 Status: 26-man roster (Pre-Arb 3)

Zac Gallen was originally acquired by the Diamondbacks at the 2019 Trade Deadline as an underrated pitching prospect in exchange for a high-ceiling infielder prospect in Jazz Chisholm. Both players have gone on to provide value to their respective new teams in the best ways they can hope for. Gallen came off a breakthrough 2019 and followed up with a Top-10 Cy Young finish in 2020. Expectations were high that Gallen would be an anchor to the starting rotation for the 2021 season.

That did not happen, as his season started with a fracture in his pitching forearm sustained while hitting in Spring Training. Gallen would miss the first two weeks of the season, but would return for the team’s final game of their first homestand against Oakland. After making 5 solid starts, Gallen was placed on the injured list again due to the dreaded “Right Forearm Tightness”. Ultimately it led to nothing more and Gallen would return on June 17th against San Francisco. After hitting a rough patch in his next 4 starts, Gallen would suffer a different injury, a hamstring, and was placed on the IL for a 3rd time. That would be his last trip, as he would be activated after the All Star Break and would make 14 straight starts to close the season.

On the season in total, Gallen delivered a 4.30 ERA over 121 13 innings, good for 2.1 bWAR. Given the expectations from 2020, it was a drop off from his 2.5 bWAR in 12 starts, which would be good for 6 WAR had he undergone a normal starter workload. Gallen is somewhere between those two extremes when everything settles, although he’s capable of putting together All-Star caliber campaigns. When healthy, he is the team’s most productive starting pitcher and perhaps the team’s best trade chip although with 4 years of control left there is no reason to make any moves with him.

Gallen’s ability to mix up four above-average, five if you want to count a slider vs. RHB, to plus pitches makes him a tough matchup for any batter. When going good, he can dominate with just the fastball and change-up, both plus pitches in their own right, while mixing in his breaking stuff for weak contact or whiffs. 2021 also saw Gallen use his secondary stuff less and focus more on establishing the 4-seamer, likely a result of him falling behind in counts against hitters and chasing strikeouts instead of just getting the hitter out when ahead. One thing that seems to be a speed bump is his ability to consistently finish off hitters when ahead with 2 strikes. That’s the one area he’ll need to improve on to take the next step of his development.

Going into 2022, I still have Gallen projected to be a 4-5 WAR pitcher if he’s able to make 30+ starts in the season. Some minor elbow trouble and the fact he relies on a cutter does give me a bit of pause for anticipating a future elbow injury, but Gallen has been able to avoid major injuries to this point. The team will need him to anchor the rotation for the next 2-3 seasons while the team gets some of their top pitching prospects acclimated to the MLB level.