Kenny Castillo’s AFL Opportunity Could Define His Diamondbacks Future
Kenny Castillo is a name that, until about a week or two ago, most Diamondbacks fans had likely never heard of.
Kenny Castillo is a name that, until about a week or two ago, most Diamondbacks fans had likely never heard of.
Even now that the Arizona Fall League has officially kicked off and the various rosters are taking the field, many are still entirely oblivious to who Castillo is, which is sort of ironic given how long he has been with the organization and how much coverage the minors have gotten over the last two years.
Castillo joined the Diamondbacks back in 2021 as a 17-year-old in the Dominican Summer League. A projectable, lanky youth, Castillo possesses a strong throwing arm that he enjoys showing off. Castillo has moved rather steadily through the farm ranks since being signed, essentially moving up a tier each season.
In 2023, Castillo received a late promotion to low-A Visalia. Then he spent all of 2024 there before being promoted to A+ Hillsboro for the 2025 season. Alas, as has been the case with so many catching prospects to go through the Arizona farm system, Castillo is a glove-first catcher - in the most traditional sense.
With a pair of injuries limiting him to 65 games with Hillsboro, the D-backs sent him out to the Arizona Fall League. Castillo said it was the first season of his career that he dealt with injuries.
What will help Castillo out in Arizona is his familiarity with many of the pitchers the D-backs sent. In the last two seasons, he's caught David Hagaman, Jacob Steinmetz, Yordin Chalas, and Lorenzo Encarnacion. He'll also reunite with his pitching coach, Tyler Mark, who was with Hillsboro in 2025.
"We played together in the season, so we had a good connection. We're working with the pitching coach. The pitching coach is Tyler Mark. So he's working with us. So we try the best right here for the fall league."
Castillo has the defensive nous to control the running game and to make the opposition be very careful with how they use bunt plays. On the other hand, Castillo’s OPS in Hillsboro for 2025 was merely .615. That’s down from the .701 OPS he sported playing the entire season in hitter-friendly Visalia in 2024.
Castillo is a bit heavy-footed, limiting his ability to leg out extra base hits. His in-game power is also on the lighter side. This pegs Castillo as a station-to-station player who usually will need multiple additional hits to score. He does control the strike zone capably with a strikeout rate that bounces around between 20-24%, but usually trends to the lower of the two.
As Castillo lacks any significant power, his walk rate is a bit on the lighter side, around 6%. This however seems to be an area in which he is seeing improvement, which would help him quite a bit, as a simple rise in his on-base percentage could make a massive difference in how he projects moving forward. He homered in Thursday's contest and tagged three balls over 100 MPH.
Castillo has been around long enough now that he is Rule-5 eligible. However, his lack of hitting development and the fact that he has never seen a pitch above A+ ball means there is no particular reason to protect him on the 40-man roster.
Right now, he’s in the position where he needs to make the most of his assignment to the AFL. If he can show some good signs in this more competitive environment, then Castillo may find himself making the step up to AA Amarillo in 2026 (though he likely starts in Hillsboro again).
If he continues to struggle with the bat, Castillo may find himself playing the role of organizational filler in A+ ball. Still, having five years of pro ball experience despite only turning 21 a mere five months ago leaves Castillo with another year or two to further develop before there is any real pressure on him.
If he continues to show positive development behind the plate as a capable receiver who controls the game well, he could eventually develop into a back-up option. But, for that to happen, his bat is going to need to improve. Right now, he’s still falling short of Jeff Mathis and Jose Herrera territory.
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Michael McDermott
