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Jun 1, 2025; Phoenix, Arizona, USA; Arizona Diamondbacks pitcher Cristian Mena (64) comes in to pitch the sixth against the Washington Nationals at Chase Field. Mandatory Credit: Allan Henry-Imagn Images Allan Henry-Imagn Images

D-backs' Internal Rotation Depth Presents Major Concern

Originally posted on Arizona Diamondbacks on SI
By Jack Sommers | Last updated Oct 12, 2025 8:01 PM ET

The Arizona Diamondbacks enjoyed a fair amount of good health in the rotation in 2025, with the obvious exception of Corbin Burnes injury.

With Burnes unavailable at least until the All-Star break, and the departures of Merrill Kelly and Zac Gallen, the D-backs are left with only three bonafide starters to fill out their rotation.

Those starters are Ryne Nelson, Brandon Pfaadt, and Eduardo Rodriguez. At the very least, the Diamondbacks need to fill two rotation spots by the start of the 2026 season. Since the team is cutting payroll, it appears it will be difficult to fill both those spots via free agency or even trade.

Arizona Diamondbacks' Internal Rotation Options

It stands to reason that the team will fill the fourth rotation spot externally, but the fifth spot could possibly be filled by an internal option.

Perhaps a standout spring training could land a pitcher with an unexpected rotation spot. In this article we take a look at who some of those options might be. The list is limited.

The table below includes only players that reached Triple-A Reno this year. Players that have not yet pitched above Double-A are not included. The D-backs are very unlikely to place a pitcher who hasn't reached Triple-A in the rotation to start the season.

Another point to note is that due to the extreme run environment of the Pacific Coast League and the Aces' home park in Reno, we are using ERA- and FIP-. These are park- and league-adjusted stats in which 100 represents league average. Lower than 100 is better than average, over 100 is worse.

FIP is Fielding Independent Pitching, using only strikeouts, walks, and home runs allowed. It takes the variance of minor league defense out of the picture and is very helpful in evaluating minor league pitchers.

The top four pitchers on this list are the most likely to be in some sort of "spring competition." There is a line drawn to denote a second tier of depth options that have little shot to enter such a competition, let alone earn a rotation spot.

Jack Sommers

Cristian Mena is at the top of this depth chart. His 4.84 ERA and 4.53 FIP for Reno were almost 20% better than league average. He earned a call-up and threw 6.2 innings, allowing just one run on three hits in three relief appearances.

Pitching in the rain in Cincinnati in early June caused him to grip the ball too tightly, however, and altered his delivery. He ended up missing the rest of the season with a shoulder strain.

Mena is expected to be ready for spring training, and should be atop the minor league starting pitcher depth chart.

Kohl Drake is a big lefty with an even bigger fastball who came over from Texas in the Merrill Kelly trade. He dominated in Double-A for Texas and was pitching well at Round Rock for Texas in the PCL at the time of the trade. He is ranked as the top D-backs pitching prospect by MLB Pipeline.

Drake struggled with results in his first three outings for Reno, but threw four shutout innings, striking out seven in his last outing on August 20. Six days later it was revealed he had a shoulder strain, but he should be ready for spring training.

Spencer Giesting had a very strong start to his season in Double-A, earning a promotion to Reno in early June. His first 12 starts were rough, posting a 8.37 ERA and 7.34 FIP. The lefty then went on a run of five starts pitching to a 3.18 ERA and 4.18 FIP to end the season on a high note.

Dylan Ray is a right-hander with a mid-90's fastball and a good slider, curveball, and changeup. A strong start in Double-A earned him a promotion to Triple-A. He had his moments and good starts, but was often undone by the long ball, giving up 18 homers in 90 Triple-A innings.

After the above four there is Yu-Min Lin, who entered the year as the top-rated pitching prospect for the D-backs. But he struggled with command and control, leading to numerous blowups and an inflated 6.64 ERA along with a 6.57 FIP.

Lin can spin the ball really well, but without command of his 40-grade fastball he will struggle to advance.

Billy Corcoran and Roman Angelo are depth options down the road midseason if the team needs long relief help. If either of them make any starts for the D-backs in 2026 something has gone very wrong.

Not listed at all is Yilber Diaz. After some horrific control issues, he was demoted mid-season to Double-A to work out of the bullpen.