The Rangers have signed right-hander Diego Castillo to a minor league contract, according to Castillo’s player page on MLB.com. The details of the the deal aren’t clear, but presumably include an invite to big league Spring Training.
Castillo, 30 next month, made his big league debut with the Rays back in 2018. Early in his career Castillo found success as a solid middle reliever for Tampa, with a 3.30 ERA and 3.53 FIP in 125 1/3 innings across 108 appearances (including 17 appearances as an opener). Castillo owned a solid 28.5% strikeout rate against a walk rate of 8.6% with an impressive 51.8% groundball rate. Among all relievers with at least 100 innings of work across the 2018-19 seasons, only Luke Jackson, Jace Fry and Ryan Pressly struck out more batters while posting a groundball rate north of 50%.
Impressive as the first two seasons of his career already were, Castillo found another gear headed into the shortened 2020 season when he posted a sterling 1.66 ERA across 21 2/3 innings of work with a whopping 60.4% groundball rate. Castillo’s success during the shortened seasons saw him establish himself as a quality set-up option at the back of the Rays bullpen, resulting in the club dealing him to the Mariners the following summer. From 2020-22, Castillo posted a 2.95 ERA (134 ERA+) despite an elevated 3.84 FIP thanks to a 27.8% strikeout rate and a 49.7% groundball rate.
Unfortunately, things came off the rails for Castillo entering the 2023 season as the righty struggled to a 6.23 ERA across 8 2/3 innings of work for Seattle early in the year, resulting 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 of work at the Triple-A level 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.
Brutal as Castillo’s performance was in 2023, his addition could provide a significant boost to the Rangers if he’s able to re-establish himself as a quality set-up arm or even as a solid 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, even before the departures of Aroldis Chapman, Will Smith, and Chris Stratton in free agency.
While Jose Leclerc is a strong back-end option and the likes of Kirby Yates and Brock Burke could be valuable pieces, Texas will need contributions from others outside of that trio to improve upon their 2023 bullpen ERA of 4.77. A rebound for Castillo would go a long way to achieving that goal, but for now the right-hander figures to enter the spring with competing for a spot in the club’s bullpen with the likes of Grant Anderson and Jake Latz.