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2019 Arizona Diamondbacks Reviews: #9, Zac Gallen

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An unknown prior to 2019, the Dbacks traded their top prospect for Zac Gallen and he delivered in spades.

San Diego Padres v Arizona Diamondbacks Photo by Jennifer Stewart/Getty Images

Rating: 7.52

Age: 24

2019 Stats: 15 GS, 80 IP, 2.81 ERA, 3.61 FIP, 10.80 K/9, 4.05 BB/9, 0.90 HR/9, 1.6 fWAR, 2.5 bWAR

2019 Salary: $583,500

2020 Salary: Pre-arbitration until 2023

It’s July 31st and the MLB Trade Deadline is less than a couple hours away. Many Dbacks fans are on the edge of their seats, frequently refreshing mlbtraderumors.com and Twitter waiting to see if Zack Greinke or Robbie Ray have been traded. All of a sudden, Twitter pops up: The Diamondbacks have acquired Zac Gallen, and it was later revealed that we traded our #1 prospect, Jazz Chisholm, to complete the trade.

What? Who?

I had no idea who Gallen was when we first acquired him and I’m sure many other fans were just as confused as I was. But don’t let his lack of notoriety fool you - Zac Gallen was a breakout pitcher, having complete dominated AAA in a year where video game numbers were the norm, and he continued to find success at the MLB level.

Now, it’s the end of the season and Gallen is 9th on this list despite only playing with the team for less than half a season. The latest ZiPS projections project Gallen as the best pitcher on the team for 2020. It was a very interesting trade but Gallen looks like he has the potential to be a top-of-the-rotation pitcher thanks to his excellent strikeout rate paired with a superb batted ball profile.

2019 Review

Zac Gallen was initially drafted by the St. Louis Cardinals in the 3rd round of the 2016 MLB Draft - an indication that he was at least a solid pitching talent out of college. The pre-draft reviews of Zac Gallen all seem to indicate he had 3 average pitches coming out of college but with fringe velocity. He had that good “feel/command” that seemed typical of St. Louis Cardinals pitchers. However, in December of 2017, Gallen was traded along with 3 other players to the Miami Marlins in exchange for Marcell Ozuna. Going into the 2018 season, FanGraphs had Gallen as the #12 prospect in their organization and again, noted that he had 3 average pitches and good command, but lacked the velo (sitting 91-93 MPH and topping out at 94 MPH) and the “stuff” to be much of anything in the MLB - giving him a FV of only 40.

However, things changed for Gallen in 2019. He found some extra velocity - his fastball averaged 93.11 MPH per Brooks Baseball, increasing as the season went on, and maxed out at 97 MPH. This helped make his fastball really good - per FanGraphs, it ranked 26th out of 132 starting pitchers with at least 80 innings pitched. He paired this with a filthy changeup - the third best in this same sample - and an effective curveball (35th), all of which led him to being one of the better strikeout starting pitchers in 2019 (22nd out of 132 at 28.7% K%).

The results for Gallen’s improvements were first seen in the PCL (AAA), which as mentioned above, was pretty much a video game simulation all season long. In 91.1 IP in the PCL, Gallen pitched to a 1.77 ERA, with 11.0 K/9 against 1.7 BB/9 and 1.0 HR/9. His 33.6% K% was nearly SEVEN points higher than the second-best in the PCL (26.8%). That’s utterly insane.

His dominance carried over to the MLB after his call-up on June 20th, 2019. Gallen would pitch 5 innings against the Cardinals - the team that drafted him - giving up 1 run and striking out 6. He’d make 7 starts in total for the Marlins, pitching 36.1 IP with a 2.72 ERA. His numbers with the Diamondbacks were similar - 8 starts, 43.2 IP, 2.89 ERA. His best game would come on September 4th against the Padres - 7 scoreless innings with 8 strikeouts, allowing only 1 walk and 1 hit. An incredibly successful campaign for the young right-hander.

I want to make a quick note of Gallen’s batted ball profile. His xwOBA finished in the 75th percentile (meaning he was among the top 25% percent). K% and BB% play a large factor in xwOBA but so do your batted ball results. Gallen was in the 81st percentile for K%, but was also 75th percentile for exit velocity, 83rd percentile for xBA, and 71st percentile for xSLG. This doesn’t necessarily mean he will be this good last year and it explains why his ERA was slower than his FIP. But, it’s also an indication that batters struggle to make good contact when they do actually hit the ball. This combination is what makes Gallen so intriguing.

2020 Outlook

Zac Gallen will undoubtedly open 2020 in the starting rotation, barring injury. He could very well be the best pitcher on the Dbacks roster next season, with ZiPS projecting him for 3.2 fWAR vs 2.7 fWAR for Robbie Ray (next-highest on the team). Gallen is only 24 and the team has him for 6 more seasons of control - he is looking to be a rotation staple for years to come.

The upside looks to be very high on Gallen - he has a strong, high-RPM fastball that induces both a lot of whiffs and weak contact and complements that with at least two, if not three, above-average secondary pitches. Gallen has shown a lot of composure and pitching ‘feel’ - he has shown he can manipulate his slider/cutter in a variety of ways - but sometimes appeared to struggle with trying too hard, which led to wildness. This is generally pretty common among young pitchers and something that we can hope will improve as he matures.

The scouting community still isn’t sold on Gallen going forward, but the underlying data all suggests he has really strong stuff. If he can maintain his level of strikeouts and strong batted ball data while improving his walk rate, he’s going to be an ace. If he regresses in one of those two areas, he will probably end up more as a #2/#3. It’s pretty clear that he has the stuff to regularly miss bats in the MLB, but will he continue to be hard to hit as well? Time will tell.