Castillo begins his first season with the Ducks and 12th in professional baseball. The infielder reached the Major Leagues with the San Diego Padres in 2021, picking up his first MLB hit and run batted in with a pinch hit RBI single off St. Louis Cardinals pitcher Genesis Cabrera on May 16 at Petco Park. In addition to the Padres, the Dominican Republic native has played with the Cleveland Indians, Toronto Blue Jays and Kansas City Royals organizations, reaching Triple-A with Cleveland and Kansas City. He has compiled a .263 career batting average with 32 home runs, 321 RBIs, 409 runs, 840 hits, 154 doubles, 35 triples and 124 stolen bases in 903 games.

The 28-year-old was named a Florida State League Post-Season All-Star in 2018 with Dunedin (A+, Blue Jays), hitting .304 with five homers, 44 RBIs, 41 runs, 118 hits, 25 doubles and eight triples that season. He was also named a Texas League Mid-Season All-Star in 2019 with Amarillo (AA, Padres), finishing the year with a .313 batting average, a .347 on-base percentage, eight homers, 57 RBIs, 62 runs, 135 hits, 30 doubles, five triples and 15 stolen bases. Most recently, the switch-hitter played with Acereros de Monclova of the Mexican League in 2023. In eight games, he totaled a homer, three RBIs, a run and a walk. Castillo was originally signed by Cleveland Indians as an international free agent in 2012.