Castillo, 27, hit .319 (403-for-1,265) with 75 doubles, 11 triples, 51 home runs, 99 walks, 256 runs scored, and 76 stolen bases in 360 games over five seasons in Cuba's major league, Serie Nacional. He spent all five campaigns with his hometown team, Ciego de Avila, and posted a career .383 on-base percentage, .516 slugging percentage, and .899 OPS while appearing primarily in center and right field.
The 5-foot-9, 205-pound Castillo last played in Cuba during the 2012-13 season and hit .274 with six doubles, two triples, six homers, and 29 RBI over 68 contests in which he struck out fewer times (29) than he walked (31).
During the 2010-11 season, the right-handed batter set career highs with 22 home runs and 95 RBI. The following season, 2011-12, he hit .342 in 113 games with 60 extra-base hits, including 21 homers, helping Ciego de Avila to the Serie Nacional Championship.
In 2011, Castillo also represented Cuba in the Baseball World Cup and the Pan American Games. He established residency in Haiti before signing with the Red Sox.
In the coming days, he will report to the Red Sox' Fenway South facility in Fort Myers, FL to resume baseball activities. With the signing, the Red Sox' 40-man roster is now at 39.