ペンサコーラ・ブルーワフーズ
Contreras was called up to the Reds from the Double-A Pensacola Blue Wahoos on June 21, 2014, and made his debut the same day against the Toronto Blue Jays in the ninth inning. In nine pitches he retired the side and recorded his first major league strikeout. Contreras was released by the Reds on March 15, 2016.