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2020 Arizona Diamondbacks Reviews #1: Zac Gallen

Zac Gallen Was The Most Valuable Player on the Diamondbacks in 2020

Arizona Diamondbacks v Houston Astros
Background: HOUSTON, TEXAS - SEPTEMBER 18: Zac Gallen #23 of the Arizona Diamondbacks pitches in the first inning against the Houston Astros at Minute Maid Park on September 18, 2020 in Houston, Texas.
Photo by Bob Levey/Getty Images


On July 31st, 2019, the Diamondbacks acquired Zac Gallen from the Marlins for shortstop Jazz Chisholm. Or as I saw it, the Diamondbacks traded away future superstar infielder, and player I befriended through an unpublished interview, Jazz Chisholm, for some guy who had already been traded once, Zac Gallen. Obviously, at the time I was a bit biased, as it was a good trade then, and it’s looking like an even better trade now for the Diamondbacks.

While Jazz has continued to struggle with batting average and strikeouts, Zac Gallen is blossoming into a potential ace for the Diamondbacks, and the numbers are trending in the right direction.

The 2020 Season

Zac Gallen was fantastic in his 12 starts in 2020, putting up 72 innings of quality work, putting up a 2.75 ERA with 1.11 WHIP. Gallen’s peripheral statistics were all excellent; While his 10.25 strikeouts per nine (K/9) innings is a slight dip from 2019, it’s still excellent and well above average. His 3.13 walks per nine innings (BB/9) wasn’t great, but was a nice improvement from the 4.05 he had put up in his 2019 debut. His homeruns per nine (Hr/9) did jump up slightly from .90 in 2019 to 1.13 in 2020, but that’s well within the range of statistical noise. Gallen benefited from a bit of a luck with his .266 batting average on balls in play (BaBIP), which was slightly below his .284 BABIP in 2019, and his career .275 BABIP. (Note:: The career BABIP number I’m using includes his 2020, which obviously lowers that number. If you exclude his 2020, that number would be higher.)

According to Baseball-Reference, Zac Gallen was the most valuable player on the Diamondbacks, with 2.7 bWAR. That’s a full win better than the second most valuable player, Nick Ahmed, who had 1.6 bWAR. He was also almost twice as valuable as the next most valuable pitcher, Merrill Kelly, who was worth 1.4 bWAR. wasn’t as bullish on Gallen, ranking him second with 1.5 fWAR, behind Cole Kalhoun’s 1.8 fWAR. Fangraph still had him as the most valuable pitcher though, with almost a full win more valua than the second most valuable pitcher, Merrill Kelly, who had 0.6 fWAR.

Future Outlook and 2021 Projections

As usual, I sought the Snakepit staff’s insight for this article, and Jim McLennan, Jack Sommers, Makakilo, and Michael McDermott all gave me their hot takes.

Jim noted that given Gallen’s career 3.64 FIP is nearly a run higher than his career 2.78 ERA, it might be wise to temper our expectations of Gallen. A 3.64 ERA isn’t terrible, but it’s certainly not at the level of a front of the line starting pitcher. Looking through Gallen’s ERA, FIP, and xFIP on Fangraphs, one thing becomes apparent; Every year outside of his first year in the minors, he has outperformed his FIP and xFIP by at least half a run, with the most drastic difference being in 2019, when Gallen put up a 1.77 ERA while having a 3.36 FIP and a 3.62 xFIP. It appears that Gallen might just be one of those pitchers where FIP is not a real indicator of future performance, and will regularly outperform it.

Jack, Michael, Jim, and Makakilo all noted that Gallen will have to work on his command and reducing his walk rate. It’s largely agreed that Gallen left on base percentage (LOB%) will regress - but what is not in agreement is, will he regress with his .BABIP? Michael put forward the suggestion that Gallen legitimately suppresses BABIP via an elite fastball/change up combo, and an above average curve. He also noted that although his 4-seamer, curve, and change provided close to elite results in 2020, his cutter saw some poor results (.356 wOBA/.351 xwOBA).

However given that it wasn’t hit particularly hard (84 MPH average exit velocity), it likely is more a command issue than a pitch quality issue. Michael also noted that without that cutter, Gallen’s ceiling may be a number 3 starter. But if he can improve the quality of that pitch, he is a potentially an elite level “ace”. Additionally, I agree with his assessment that it is unclear if Gallen’s true talent level is a 2.7X ERA pitcher. Given that 2020 was such a small sample size, a full season’s worth of starts in 2021 will be a big determining factor of what his actual ceiling is.

Jack noted that Gallen will eventually regress in LOB% and BABIP, and added that “Greg Maddux had a BB/9 rate above 3 for his first 5 seasons . He didn’t really lower it until he was 25. Gallen doesn’t have anywhere near the innings total and is not a comp to Maddux. I just bring it up to show that the walk rate can potentially drastically improve. I’m hopeful, even confident, it can.” What’s interesting is that the ZiPS projection system for the 2020 season actually did think Greg Maddux was a comp, albeit a Greg Maddux before he became Greg Maddux,

For 2021, ZiPS projects Gallen to be the best pitcher on Arizona’s pitching staff, and the only pitcher projected with an era below 4. Although a 3.74 ERA sounds underwhelming, that’s still a 123 ERA+ and worth 3.6 WAR. MARCEL is a little more bullish on Gallen, projecting a 3.44 ERA.

I reached out to Zac Gallen on twitter for comment, but I have yet to receive a response. I’ll edit in any comment if does respond.