Arizona Diamondbacks 2024 Player Review: Humberto Castellanos

A familiar face to the D-backs' organization played a small, yet solid role in 2024.

Jul 6, 2024; San Diego, California, USA; Arizona Diamondbacks relief pitcher Humberto Castellanos (54) celebrates on the field after defeating the San Diego Padres at Petco Park. Mandatory Credit: Orlando Ramirez-Imagn Images / Orlando Ramirez-Imagn Images

This article is part of a series chronicling the individual seasons of players who appeared for the Arizona Diamondbacks in 2024.

Reviews for players that still have rookie eligibility for 2025 will appear in our prospect season reviews. Players are presented in the reverse order of their aWAR, an average of Baseball Reference and FanGraphs WAR.

RHP Humberto Castellanos

2024 Contract status: Pre-Arb, $740,000, prorated $167,953 for time spent on MLB roster

Humberto Castellanos 2024 and career stats / Alex D'Agostino | Diamondbacks On SI

The Diamondbacks are no stranger to right-handed pitcher Humberto Castellanos, as he first joined the organization back in 2021, but battled injury for the greater part of the last two seasons. He pitched in the Mexican League, and spent a majority of his time with the D-backs in Triple-A Reno, though he did make nine starts for Arizona in 2022.

In 2024, the D-backs invited him to Spring Training as a non-roster invitee. Castellanos failed to make the Opening Day roster, and spent two months with the Aces, making nine starts, and pitching to a 4.57 ERA in the hitter-friendly Pacific Coast League.

But on June 6, left-handed pitching prospect Blake Walston was placed on the surprise 15-day Injured List with left elbow inflammation. Alongside Walston, left-hand long reliever Logan Allen was optioned to Triple-A.

With a new need for both pitching depth and a long reliever, the D-backs selected Castellanos' contract, with the idea that the Triple-A starter would provide relief depth, not starts.

Castellanos made his first appearance on June 7 against the San Diego Padres, after starter Brandon Pfaadt was hit around for five earned runs over 5.1 innings. With the D-backs' bullpen taxed, and a 5-0 deficit, Castellanos came in to provide cleanup.

Unfortunately, he was knocked around as well, surrendering five hits, two walks and a hit-by-pitch, leading to five earned runs over 2.1 innings of relief. He was returned to Reno the next day.

After two more starts for the Aces, the D-backs called upon Castellanos once more on June 28. He wouldn't make an appearance until July 5, where he pitched 2.1 scoreless innings, also against the Padres.

His first three major league appearances would all come in San Diego, as he pitched the very next day on July 6. In a wild contest, the D-backs and Padres traded back-and-forth blows, heading into extra innings tied at 4-4.

Arizona would score three runs in the top of the 10th, taking a 7-4 lead. Right-hander Thyago Vieira entered for the save with the D-backs' bullpen depleted, but would only retire one batter, surrendering two walks and a double, pulling the score to 7-5.

With Vieira rattled, the D-backs turned to Castellanos, who recorded a strikeout and flyout to end the game, picking up his first career save in a critical situation.

Castellanos would only make four more appearances for the D-backs. While mainly in cleanup duty, the right-hander only allowed one run over six of his seven appearances. His five-run blowup in the first major league action of the year contributed to his final ERA sitting at 5.23, but it was 1.13 over his other six outings.

Additionally, his FIP, even including his one poor outing was merely 3.55, suggesting some bad luck. His FIP over his six solid outings was 2.79.

But Castellanos would be sent back to Reno on July 23. He was recalled and optioned back two more times, but never made another major league outing for the major league club. On August 11, he was designated for assignment, but cleared waivers and was outrighted to Reno five days later.

He continued to pitch well as a starter in Triple-A, pitching to 1.83 and 3.42 monthly ERAs over August and September in a tough hitter's environment. He finished with a 3.81 ERA with the Aces, with just a .220 average against and 1.18 WHIP in the minors.

2025 Outlook

2025 Status: Free Agent

On October 14, Castellanos elected Free Agency. Certainly, he has a relationship with the D-backs' organization, and has found some success with Arizona's affiliates and major league club.

There's a decent chance he signs with another organization, and at only 26 years old, has potential to see major-league action again at some point. It's not out of the question he returns to the D-backs in some capacity, and would be valuable long-relief depth, or even an emergency start in the event of injury or severe need.

His stuff has moderate-to-below-average movement, and his primary fastball (sinker) barely manages to exceed 90 MPH. If his location is on, he can be effective, but his stuff might not play for long at a major league level.

Still, he did appear to be able to succeed as a long-man (albeit in a small sample size) and could see opportunity in 2025, with the D-backs or elsewhere.

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