A change in AIBA's rules preventing boxers under the age of 19 from competing in senior tournaments directly affected Cintrón. Despite being unable to compete internationally, he remained active in Puerto Rico and trained throughout 2013. Cintrón entered the Torneo Isaac Barrientos and won the flyweight national championship by defeating fellow Olympian Janthony Ortiz in the finals. Despite losing, Ortiz was sent to the 2013 AIBA World Boxing Championships due to the age criteria. At the 2013 Juan Evangelista Venegas Olympic Cup, Cintrón defeated Leonardo Baez of Mexico by unanimous decision in the finals. He entered the 2014 Isaac Barrientos tournament, debuting with a victory over Orlando González. Cintrón advanced by knocking Carlos Caraballo out in the semifinals. In the finals, he was matched against Ortiz, winning a unanimous decision after scoring a knockdown.