The Riskiest Move: Analyzing What the Diamondbacks Have in Zac Gallen

Hours before the trade deadline, it seemed as if the D-backs might have a very quiet day. While MLB Network Insider Jon Morosi reported that they were “focused intently on selling conversations,” trade talks around Robbie Ray, the most oft-rumored name, had stalled, and no other major rumors had been born. But when the dust settled, the Arizona’s top pitcher and top prospect were no longer with the team. Zack Greinke’s departure is what is making all the headlines, rightfully so, and it signals the end of the era for the five stars—Greinke, Paul Goldschmidt, Patrick Corbin, J.D Martinez, and A.J. Pollock—who led the team to the 2017 postseason. But the trade was fairly textbook: a selling team gives up a star to a buying team for several top prospects that will help them down the line. We’ve seen this a thousand times, and we all know what it means.

What we haven’t seen a thousand times, however, is a deal like the prospect-for-prospect swap that brought right-handed pitcher Zac Gallen to the D-backs in exchange for shortstop prospect Jazz Chisholm. It’s a more gutsy decision; while most fans on a selling team will readily accept selling a major leaguer for prospects, it’s tougher to convince people on trading away a top prospect for another top prospect. Very few trades in baseball have as much uncertainty as this one. Chisholm has star potential, but it may be hidden behind a picture of an overly aggressive hitter whiffing at major league breaking pitches. While Gallen doesn’t have the same potential, he does have successful major league experience, but that may be an early-career mirage that declines once teams adjust against him. But when you give up a player with so much potential and so much control, as both the D-backs and the Marlins did, then you have to be awfully confident that what you are getting is better than what you are giving. And either the D-backs or the Marlins are probably going to be wrong.

So what do the D-backs see in Gallen that gives them the confidence to trade away Chisolm? Part of it, surely, is about reducing risk. Gallen already has made the majors, and in a very limited sample size succeeded to the tune of a 2.72 ERA and a 4.38 DRA, the latter ten percent better than league average. But there are also a lot of flaws in his limited sample size that are both exposed by more advanced stats and heed warning about future performance. His 11.9% walk rate tops every qualified pitcher, including Robbie Ray (4th), and his 31.8% ground ball rate is the lowest of that same group, including Robbie Ray (13th). Unsurprisingly, Gallen has struggled to get deep into starts, finishing the sixth inning in only the two most recent of his seven starts. While his strikeout rate (13th) has dazzled, very few pitchers have survived with that formula in the majors, except for, you guessed it, Robbie Ray. 

So did the D-backs just trade for a younger version of Robbie Ray, who always seems to have star potential but is held back by issues that seem unfixable? No. This is probably the time to warn you about the sample size we are dealing with, only seven games and less than forty innings pitched, so regression should be expected in every area mentioned above. Scouting reports laud his control, so it’s odd to see him walking so many batters out of the gate. Strangely, the reports also are in contrast to his early season debut when it comes to his stuff; his changeup, described as his weakest pitch, has been his most dominant in terms of whiffs, ground balls, batting average against, and slugging percentage against. This creates a puzzling picture for the D-backs to sort through, but clearly they believe they’ve seen through the fog to make a bet on the righty, who just turned 24 on Saturday.

Ideally, the D-backs will be able to combine his high strikeout rate that he’s shown this season with better control to form a pitcher better than what most think he is capable of, but the ideal rarely ever coalesces. Currently, he’s just trying to find the pitch mix that works best for him. He’s gradually been dropping his slider usage over the season, throwing it over 30% of the time in his first two starts and under 10% in his most recent two. Over the last two starts, he’s also thrown his changeup more—setting a season-high with 28 (26.7%) in his seven inning gem the day before the deadline. In fact, his changeup usage has been a solid predictor of his success this season; in the four games where he’s thrown at least ten each, he has a 1.88 ERA, but in the others, his ERA jumps to 4.38. As mentioned above, it’s been his most effective pitch, but surprisingly, he doesn’t tunnel it well with his fastball, usually a requirement for an effective change. In fact, his arm slot for all his pitches leaves plenty to be desired:

In his last start, his changeup release point was almost four-tenths of an inch away from that of his fastball, and while that seems small, it could be enough to allow hitters to pick up on which one is which. However, Gallen does an excellent job putting the pitch exactly where he wants it—just below the zone. To the hitter, it would seem as if the pitch starts just above the bottom of the zone, forcing them to swing to avoid a strikeout, before it darts just below the zone to where the hitters can barely touch it:

It’s not only the changeup that Gallen locates well. His fastball, while also used as his main in-zone option, is commonly thrown up and out of the zone, and his breaking pitches are nested below the zone an impressive 47% of the time. For Gallen, his command shines not by dotting the corners of the zone but by just missing the zone in the most likely spot for a swing and miss. This comes with a high cost in terms of walks. It’s strange that Gallen doesn’t hit the zone more often when he falls behind in counts considering his command; perhaps he is afraid of giving hitters a good shot at attacking his non-elite stuff. At this point, it’s holding him back from being able to consistently dazzle, and for the time being, it presents a rare scenario of a pitcher who can locate the ball well but not prevent walks.

With such a bold move as trading away the toolsy Chisholm, it is imperative that Gallen performs at least to his expected role—a third or fourth pitcher in an average rotation. Certainly, the move is influenced in part by Jazz’s contact issues, which could prevent him from ever taking a firm grip on a starting position, and Gallen’s major league success is a pleasant contrast to Chisholm’s minor league struggles. By locating his pitches out of the zone but close enough to appeal to hitters, Gallen has racked up the strikeouts this season, but whether by fear of being crushed or a fluke of small sample size, he hasn’t been able to throw true strikes enough to prevent a high walk total from accompaining it. To take the next step, he’s likely going to have to figure out how to hit the zone without being hit, but even if he can’t, the D-backs will have the luxury of having one fewer pitching slot to fill until the quarter-century mark passes.