Castillo went 2-for-4 with a solo home run in Monday's 6-1 loss to the Brewers.
The rookie infielder took Eric Lauer deep in the top of the fourth inning for his first long ball in the majors. Castillo has been seeing most of his action at second base, and the 24-year-old is batting .310 (9-for-29) through his first eight big-league games as he auditions to potentially be the future double play partner for Oneil Cruz.