スプリングフィールド・カージナルス
Valera signed with the St. Louis Cardinals as an international free agent in May 2010. He made his professional debut with the Venezuelan Summer League Cardinals. He started 2014 with the Palm Beach Cardinals and was promoted to the Double-A Springfield Cardinals during the following season. Valera began 2016 with the Springfield Cardinals and was then promoted to the Memphis Redbirds, where he batted a combined .304 between both teams.