Rangers Sign Diego Castillo to Minors Deal

December 26, 2023

The Texas Rangers have added right-hander Diego Castillo to their mix for 2024 by signing him to a minor-league deal. The news of the signing surfaced in an unusual fashion as it was first reported on Castillo’s player page on MLB.com. For the moment, the exact details of the the deal aren’t clear, but presumably include an invite to spring training.

Middle Relief Option

Castillo, who turns 30 next month, will add some depth to the Rangers’ bullpen. This is an area that the Rangers hope to improve upon. In 2023, their bullpen finished 24th in the majors in ERA (4.77) in the regular season.

Diego Castillo made his major league debut with the Tampa Bay Rays in 2018. Early in his career Castillo found success as a middle reliever for the Rays. He posted a 3.30 ERA and 3.53 FIP in 125 1/3 innings. This translated into 108 appearances, including 17 appearances as an opener. Castillo owned a 28.5% strikeout rate against a walk rate of 8.6%. He also had an impressive 51.8% ground ball rate. Among all relievers with at least 100 innings across 2018-19, only Luke Jackson, Jace Fry, and Ryan Pressly struck out more batters while posting a ground ball rate north of 50%.

Success in 2020

Impressive as the first two seasons of his career already were, Diego Castillo found another gear headed into the shortened 2020 season. He posted a minuscule ERA of 1.66 across 21 2/3 innings with a 60.4% groundball rate. His success during the shortened seasons saw him establish himself as a good set-up option at the back of the Rays’ bullpen. This resulted in the club dealing him to the Seattle Mariners the following year. From 2020-22, Castillo posted a 2.95 ERA despite an elevated 3.84 FIP thanks to a 27.8% strikeout rate and a 49.7% groundball rate.

Unfortunately, things fell apart for Castillo entering the 2023 season. The righty struggled to a 6.23 ERA across 8 2/3 innings for the Mariners. This resulted in the club outrighting Castillo off the roster in early May. The right-hander’s struggles continued in the minors throughout the year, as Castillo posted an ERA of 5.13 across 47 1/3 innings at Triple-A Tacoma across the remainder of the season. Castillo became a minor league free agent back in October, giving the Rangers the opportunity to pick him up on a non-roster deal.

Significant Boost

As bad as Castillo’s performance was in 2023, his addition could provide a boost to the Rangers. The hope is that he’ll be able to re-establish himself as a quality set-up man or a middle reliever. Entering the 2023 season, Castillo sported a career 3.12 ERA and 3.69 FIP. Meanwhile, the Rangers had one of the worst relief corps in the entire league last season. The departures of Aroldis Chapman, Will Smith, and Chris Stratton in free agency have had Rangers front office officials working diligently to fill those holes.

Jose Leclerc is a strong back-end option and the likes of Kirby Yates and Brock Burke could be valuable pieces. However, the Rangers will need help from others outside of that trio to improve upon their 2023 season. A rebound for Castillo would go a long way to achieving that goal. For now, the right-hander figures to enter the spring competing for a spot in the Rangers’ bullpen. He’ll go up against the likes of Grant Anderson and Jake Latz.