Arizona Diamondbacks sign lefty reliever José Castillo to a minor-league contract

The Diamondbacks recently signed left-handed reliever Jose Castillo, and if he can return to his 2018 form, he may become a valuable part of the D-backs’ 2024 bullpen.

Los Angeles Angels v San Diego Padres
Los Angeles Angels v San Diego Padres / Orlando Ramirez/GettyImages
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On Monday, Tim Dierkes of MLB Trade Rumors reported that the Arizona Diamondbacks have signed now former San Diego Padres left-handed reliever José Castillo to a minor-league deal with an invitation to Spring Training. It’s a low-risk move with the potential to pay dividends in 2024.

Can you provide some background?

Absolutely.

The 27-year-old lefty reliever is from Venezuela and in 2012 signed with the Tampa Bay Rays as an international free agent. He spent two years in the Rays’ system before being traded to the Padres in 2014.

In 2017, the Padres added Castillo to their 40-man roster, and on June 2, 2018, he made his MLB debut at the age of 22. His rookie season was impressive, concluding with a 3.29 ERA (2.64 FIP) in 38 1/3 innings. He struck out 52 batters and had a K% of 34.7% with a BB% of 8.0%.

However, injuries would become a problem. Castillo began 2019 on the 60-day IL with a left flexor strain, and he managed only 2/3 of an inning with the Padres before injuring the middle finger on his left hand and returning to the 60-day IL. He missed the shortened 2020 season with a torn hand ligament. Then, in March 2021, the Padres announced that Castillo had undergone Tommy John surgery and would miss the rest of the season. In November of that year, he was non-tendered by the Padres before re-signing with them in January 2022. He pitched one inning for the Padres in August, spending the rest of the season in Triple-A El Paso.

Castillo began 2023 with the Chihuahuas, where he struggled. In 18 1/3 innings, he had a disappointing 9.82 ERA (7.06 FIP) while striking out 22 and earning two saves. His K% was 10.80%. He was called up for one game with the Padres where he managed to record only one out, instead giving up two hits and two walks that resulted in four runs. On July 20, he was designated for assignment.

On July 25, Castillo was traded to the Miami Marlins for cash considerations, and on August 10, he was outrighted to the Marlins’ Triple-A affiliate. During his time with the Jumbo Shrip, he appeared in 19 1/3 innings over 14 games for a 5.59 ERA (3.88 FIP). He struck out 26. In October, he elected to become a free agent.

What’s the pitch mix like?

As Baseball Savant shows, Castillo has a four-seam fastball (94-95 mph) and slider with an occasional changeup. In 2018, the slider was elite as seen in this video clip from September when he struck out the side in a game against the Giants.

When Castillo’s healthy and his stuff is working, he’s an effective pitcher. So far, however, consistency has been evasive.

What’s in it for the D-backs?

It’s a low-risk move for them. If Castillo can stay healthy and find his 2018 form, then they have signed a valuable addition to their bullpen who provides them with some minor-league depth. Moreover, although Castillo is out of options, he has slightly more than four years of service time, which would allow the D-backs to retain him via arbitration beyond 2024.

It’s also safe to assume that D-backs pitching guru Brent Strom also has some ideas about how Castillo can address the issues he’s faced on the mound. As the Diamondbacks continue to prepare for 2024, signing José Castillo is a good move.