With four months of the minor league season in the books, there is enough of a sample size to evaluate which minor league prospects have improved their stock the most in the Diamondbacks system. I’ve highlighted one player at each level who I felt improved the most during the 2024 minor league season.
Thank you for reading this post, don't forget to subscribe!Triple-A Reno: Catcher Adrian Del Castillo
No prospect in the Diamondbacks system did more to improve his standing this season than Adrian Del Castillo. At the start of the season I had him as an intriguing prospect near the bottom of the Top 30, coming off a solid 2023 campaign. Now, he’s without a doubt a Top 10 prospect in the organization although it’s likely his eligibility runs out before the next re-ranking, as he’s an obvious candidate to take the extra position player spot in September.
While he had a solid 2023 season with Double-A Amarillo, it was tough to take his rise seriously due to questionable underlying metrics. He had a strikeout rate of 25.3% vs. a 15.1% walk rate in Double-A, then 28.9%/12.6% in Triple-A. There were too many strikeouts in that profile to consider him a top prospect in the organization, especially for one with concerns about his viability behind the plate.
In his second stint with Reno, he changed everything. He cut his strikeout rate nearly in half, down to 16.8% while maintaining a strong walk rate of 11.5%. He improved his ability to make contact on pitches in the strike zone, allowing him to put up quality extra-base hit numbers with 36 doubles and 24 home runs in the hitter-friendly Pacific Coast League before Gabriel Moreno’s injury necessitated a call-up to the major leagues.
In his early run with Arizona, he has looked solid at the plate. He’s shown a consistent approach at the plate and has not been intimidated by big situations. He’s hit two home runs, both coming in the ninth inning, that have made a major impact in those two games. He also drew a key walk that wound up setting the table for a walk-off win.
The main area of concern left with Del Castillo is his viability as a defender. He has a below-average arm behind the plate, a limitation that will cap his ability to throw out potential basestealers. Even with those concerns, he’d be a valid backup for 50-60 games in a season who provides value with the bat more so than the glove. It’ll be interesting what other avenues they’d try to get his bat in the lineup, as he doesn’t necessarily fit the traditional mold of a backup catcher.
Double-A Amarillo: Right-Handed Pitcher Yilber DÃaz
Yilber DÃaz probably has the smallest leap from start to end of the four players listed here, but it’s still a notable addition. He belongs in the conversation of some of the top pitching prospects in the organization, although the organization still doesn’t have a bona fide starting pitcher prospect since Brandon Pfaadt and Ryne Nelson both graduated last season.
In a year where most of the prospects in Amarillo either stalled, battled injuries, or flamed out, DÃaz was one of two prospects who really made his mark at this level. The other was Deyvison De Los Santos, who the Diamondbacks sold high on in July to land left-handed reliever A.J. Puk at the deadline.
The most important part was the young right-hander showed improved strike-throwing ability. While it doesn’t necessarily reflect as much in the overall walk rate, he was able to command the baseball better when in the strike zone. He’s still a work in progress on that front, but it’s less of a question of if, but when.
The strong year between Double-A and Triple-A earned him a four-start cameo. While it was obvious he wasn’t ready for a major league stint, he held his own in three of those starts and gave his team a chance to win. He has the mental makeup to be an impactful arm for the Diamondbacks long-term, but there is still the question of if the arsenal and command can be good enough to start. The slider has become a nice third pitch, but his arsenal still profiles as a power arm in the back of the bullpen.
High-A Hillsboro: Left-Handed Pitcher Spencer Giesting
Spencer Giesting was always an intriguing left-handed arm with more velocity than some of the organization’s best left-handed arms, but was coming off a so-so season in 2023 with Hillsboro. In 2024, he was downright dominant for most of the year and was deserving of more accolades than he got. He was promoted to the more challenging environment of Amarillo midseason.
In 10 starts with Hillsboro, he averaged six innings per start with a 1.50 ERA, 67 strikeouts, and 13 walks. By the time the organization decided he needed to get moved up, he was making seven-inning scoreless starts on the regular. It was clear he needed a more challenging environment.
The numbers haven’t been as good in Amarillo, with a 5.70 ERA and his walk rate doubling from 5.6% to 11.1% and the home run rate increasing from 0.30 to 1.34 per nine innings pitched. It’s a learning process that in an unforgiving environment in the minor leagues that he has to be able to execute pitches and avoid mistakes in either free passes or leaving pitches in the heart of the zone to get hammered.
Giesting features the typical lefty reliever profile with a low-90s fastball and a plus slider. That’s still probably his long term role, but the fact he was able to put up solid numbers at Age 22 at High-A pushes him more as an arm to watch to see if there are any further improvements. The ability to develop a usable changeup will be key to give him a pitch that can work to the arm side of the plate against right-handed hitters.
Low-A Visalia: Second Baseman Demetrio Crisantes
At a level where the Diamondbacks had three intriguing infield prospects from their 2022 international signing class, including two who warranted Top 10 in the organization rankings, it was a 2023 draft pick from Nogales who has stolen the show. The organization certainly saw potential in Demetrio Cristantes, signing him for a well-over-slot $425,000 to forego a commitment to the University of Arizona.
After starting the year in the complex, they moved the 19-year-old to Visalia where he has taken off. In 46 games, he’s hitting .355 with five home runs, 14 stolen bases, and a .960 OPS. He continues to show excellent strikeout and walk rates, coming in at 15.7% and 13.4% respectively. He went from a relative unknown to being in the same conversation as Cristofer Torin and Jansel Luis as the top infield prospect in Visalia.
His numbers are propped up by a .412 average on balls put into play, likely due to the quality of defense at that level combined with his own hitting ability. The BABIP will likely drop as he climbs up the system, but the strong strikeout and walk rates suggest there is some good plate discipline backing up the line.
2025 should be more telling of his long-term upside. Defensively he’s likely limited to a second base only profile, with 39 of his 63 starts this season coming there. He has 18 starts at third base and played first base at the complex last year.
Honorable Mentions
- Cristian Mena was quietly having a quality season with Triple-A Reno, with a 4.61 ERA and a 24% strikeout rate. He struggled in his first appearance, having to start in Dodger Stadium. His velocity was up to 93-97 MPH in that start, a positive sign assuming his forearm injury isn’t a precursor to needing elbow surgery. I had him ranked as the Diamondbacks’ top pitching prospect as of July.
- Dylan Ray missed the first two and a half months with an elbow issue, but has held his own with Double-A Amarillo with a 4.50 ERA and a 21.9% strikeout rate. The home run rate at that level is somewhat concerning, with a HR/9 north of 1.90 in the most homer-friendly stadium in the minor leagues as his home park.
- Landon Sims has really blossomed since moving to full-time relief. He has a 32% strikeout rate vs. a 10% walk rate with High-A Hillsboro.
- Right-hander Kyle Amendt has gotten himself all the way up to Triple-A in his first full year in the Diamondbacks organization. He posted a 53% strikeout rate in High-A then a 42% clip in Double-A. He could be a guy that gets looked at as a possible bullpen depth piece in 2025.
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Michael McDermott covers the Arizona Diamondbacks, Arizona Cardinals, and more for Burn City Sports. You can follow him on X via @MichaelMcDMLB
