- Bats Both, Throws Right
- Height 6', Weight 200 lb.
Castillo was mainly a catcher in the minor leagues, but also spent time at third base, in the outfield and elsewhere. A product of the Arizona Diamondbacks organization, he spent five seasons in their farm system. He emerged as a prospect in 2007, when he hit .302 with 31 doubles in 109 games for the Mobile Bay Bears of the AA Southern League. However, his on-base percentage was a weak .333 as he only drew 17 walks all year. He moved to AAA in 2008, playing for the Tucson Sidewinders of the Pacific Coast League, putting up a line of .254/.305/.358. On August 14, he was included in the trade that sent outfielder Adam Dunn from the Cincinnati Reds to the Diamondbacks; Castillo went to Cincinnati alongside two other prospects and was called up when rosters expanded at the beginning of September. His made his debut as a pinch hitter on September 2, 2008 and got his first major league hit the next day, also as a pinch hitter.