There Are Some Diamonds at the Back of Arizona’s Rotation

Players have reported to camp, bullpens are being thrown, and batting practice is being taken. Spring training is nearly in full swing with a full slate of games scheduled for Saturday. Every spring, the various position battles being waged on every team’s roster are often the most interesting storylines to follow.

This year, a surprising position battle opened up in Arizona. Last weekend, Mike Hazen, the general manager of the Diamondbacks, confirmed that there would be an open competition for the fifth spot in Arizona’s rotation. With Madison Bumgarner added during the offseason and Robbie Ray still in the fold, it looks like the D-backs have just one open spot. Luke Weaver should be fully healthy after recovering from his forearm strain that wiped out nearly four months of his season last year. Mike Leake, who is dealing with a fracture in his non-throwing hand this spring, likely has a spot in the rotation locked up too. Many assumed Zac Gallen, acquired by the D-backs at the trade deadline last year, would have earned that last spot with his impressive rookie campaign, but apparently that’s not the case. Instead he’ll have some competition in the form of Merrill Kelly and Alex Young.

The fifth spot in the rotation is probably Gallen’s to lose, but both Kelly and Young bring intriguing profiles to the table that make this position battle a little more interesting than it may seem. Here’s a quick look at what ZiPS sees from this trio.

On the heels of his excellent major league debut, Gallen’s projection is clearly the best of the trio. In fact, ZiPS projects him to be the best starter on the Diamondbacks. Based on these projections alone, this “battle” is shaping up to be pretty boring.

To his credit, Gallen certainly looks the part of a solid mid-rotation arm. In 80 innings last season, he posted a 3.61 FIP and accumulated 1.6 WAR for the Marlins and D-backs. But despite that sterling debut in the majors, there is a rough case to be made for caution. Gallen was aggressively promoted by the Cardinals after they drafted him in the third round in 2016. After dominating High-A across nine starts in 2017, however, he didn’t post a FIP below four at a single level until his second go-around in Triple-A in 2019. A big jump in his ability to generate swinging strikes fueled his step forward last year and he’ll need to prove that he can carry over those improvements to this season.

But don’t count out the other two contenders for this rotation spot just yet.

After washing out as a prospect in the Rays organization back in 2014, Kelly made the overseas journey to Korea, where he was quite successful across four seasons. The Diamondbacks signed him to a two-year deal last offseason. He made 32 starts in his first year back in the major leagues and compiled a park- and league-adjusted FIP just barely below league average. But the reason why he could challenge Gallen this spring is related to his performance down the stretch last year.

In September, Kelly added an extra tick of velocity to his entire arsenal. That pushed his fastball from averaging 92 mph to 93 mph, topping out at 95.6.

With that added velocity came additional whiffs. His high-spin fastballs already had above-average whiff rates prior to the last month of the season, but he pushed them even further in September. Along with his excellent curveball, that gave him three different pitches that he could use to generate swinging strikes. Through the first five months of the season, he ran a strikeout rate just a hair below 19%. In five September starts, his strikeout rate jumped to 27.6% and his FIP dropped to just 3.37. That rise in velocity provides a tantalizing glimpse of what Kelly could be.

Meanwhile, Young has steadily moved through the Diamondbacks organization since being drafted in the second round back in 2015. Even though he struggled in his second stint in Triple-A last year, he received a call-up to the majors in late June and made 17 appearances and 15 starts for Arizona. His ERA outperformed his FIP by a pretty wide margin, though much of that was fueled by a high home run rate.

Despite an arsenal that lacks raw velocity — his fastball averages under 90 mph — he was able to generate an above-average swinging strike rate in his major league debut. If we look at the raw characteristics of his pitch arsenal, we can begin to see why.

Young’s four-seam fastball is well below average but the other four pitches in his repertoire all have standout movement profiles. His sinker has excellent run and above-average sink and it pairs well with his changeup, which has a similar amount of horizontal movement but drops off the table as it reaches the plate. Those two pitches give him a solid foundation against right-handed batters. But his other two secondary pitches, a cutter that looks more like a slider and a slurvy curveball, are standout pitches as well and help him keep left-handed batters in check. The quality of his pitch movement directly coincides with his ability to generate favorable outcomes with each pitch.

For the pitch outcomes above, I’ve taken his raw whiff rates and batted ball rates, compared them to league-average rates within each pitch type, and calculated plus scores where each point above or below 100 is a percentage point above or below league average. Four of Young’s pitches run whiff rates above league average with just his four-seam fastball lagging behind. And three of his five pitches generate contact on the ground at an above-average rate. Just this quick look at his arsenal indicates that by simply ditching his four-seam fastball, Young could take a big step forward this season.

Young’s repertoire and approach are very reminiscent of Marco Gonzales. Both have a balanced pitch mix that lacks raw stuff, but they’re able to use all of their pitches well to keep batters off balance. The lack of high-end velocity probably limits his ceiling a bit, but he certainly has the tools to become a solid contributor in the rotation.

While Gallen is rightfully the front-runner in this spring competition, both Kelly and Young bring intriguing elements to the table that the Diamondbacks will have to weigh. And even if Gallen easily wins the final spot in the rotation, the reality is that both Kelly and Young will likely be called on at some point this season as attrition takes its toll on the pitching staff. A deep rotation with plenty of options is a nice luxury to have as the Diamondbacks turn their eye towards the NL Wild Card this year.