The Diamondbacks announced Friday that they’ve designated infielder Diego Castillo for assignment. His spot on the 40-man roster will go to outfielder Lourdes Gurriel Jr., whose previously reported three-year deal has now been formally announced by the club.
Castillo, 26, was traded from the Pirates to the D-backs 364 days ago, with Arizona sending minor league righty Scott Randall the other way in the deal. He appeared in just one game with the Snakes this season and went hitless in his lone plate appearance. He tallied 283 plate appearances in Pittsburgh a year prior but struggled to a .206/.251/.382 batting line in that MLB debut.
The bulk of Castillo’s 2023 season came in Triple-A Reno, where he played second base, shortstop, third base and left field over the course of 124 games. In 556 plate appearances, Castillo turned in an excellent .313/.431/.410 slash while walking more often than he struck out (17.4% versus 14.2%). In 177 career games at the Triple-A level, Castillo is a .296/.410/.407 hitter with nearly as many walks (124) as strikeouts (125).
Given his versatility, keen eye at the plate and excellent bat-to-ball skills, there’s a good chance that Castillo will draw interest from another club — if not in a trade (which seems quite plausible) then at least via waiver claim. He was never an elite prospect, but reports on the Venezuelan-born infielder have long touted his plus hit tool, even if that’s generally seen as his only above-average tool. Castillo has never swiped more than 13 bases and only has two seasons where he’s reached double-digit home runs; he hit just three long balls in 2023 despite spending the year in an immensely hitter-friendly setting.
Even if he’s “only” a contact-oriented utilityman, there’s still value to be had with Castillo. The fact that he’s being designated for assignment to make way for Gurriel’s return speaks to the manner in which the Arizona roster has deepened in a short time. The 2021 D-backs lost 110 games, but in just two years they’ve climbed to the World Series runners-up and are jettisoning a player who’d have been a veritable lock for playing time there just a couple seasons ago.
The Diamondbacks will have a week to trade Castillo or attempt to pass him through outright waivers.

 Despite Gurriel’s uneven performance in 2023, he’s been a pretty solid bat throughout his career with an above-average wRC+ every year since he debuted in the majors back in 2018. Since becoming an everyday player during the shortened 2020 season, Gurriel has slashed .279/.326/.456 with a 112 wRC+. He also receives strong marks for his defense in left field, including a +14 Defensive Runs Saves with Arizona last season. While Gurriel managed just five homers in 121 games with the Blue Jays in 2022, he rediscovered his power stroke with the Diamondbacks last year, clubbing 24 home runs to go along with 35 doubles, both career-best figures.
Despite Gurriel’s uneven performance in 2023, he’s been a pretty solid bat throughout his career with an above-average wRC+ every year since he debuted in the majors back in 2018. Since becoming an everyday player during the shortened 2020 season, Gurriel has slashed .279/.326/.456 with a 112 wRC+. He also receives strong marks for his defense in left field, including a +14 Defensive Runs Saves with Arizona last season. While Gurriel managed just five homers in 121 games with the Blue Jays in 2022, he rediscovered his power stroke with the Diamondbacks last year, clubbing 24 home runs to go along with 35 doubles, both career-best figures.
