Early years Mancuello made his league debut for Independiente in a 1–2 home defeat by
Arsenal de Sarandí on 14 December 2008. He scored his first goal for the club in a 5–1 away defeat to Lanús on 5 April 2009. He scored again on 11 April in a 2–1 win over Huracán.
Loan to Belgrano After not being considered by Independiente's coach
Antonio Mohamed in July 2011 Mancuello was loaned to
Club Atlético Belgrano for one year. On 26 October he scored his first and only goal in a 1–0 victory against
Tigre. In January 2012 Mancuello suffered an injury in a match of the
Copa Argentina which kept him out of the fields for several weeks when he was being a key player of his team.
Return to Independiente For the 2012
Torneo Clausura, Mancuello returned to Independiente. His only goal that season came in a 2–1 victory against
Liverpool in Uruguay, where he scored the equaliser. However, the club was relegated for the first time in his first season back. Independiente were soon promoted back to the Primera División after only one season in the Nacional B where they finished third and Mancuello scored two goals. On 31 August 2014, Independiente faced their
rivals Racing Club, but Mancuello scored to help Independiente to a 2–1 victory, saying it was "the most important goal of my career". After scoring 10 goals in 19 games in the 2014 season, Argentina manager
Gerardo Martino stated that he would keep Mancuello in mind for future call-ups.
Flamengo 2016 season On January 6, 2016, Mancuello was signed by Brazilian club
Flamengo for a fee of
R$12 million. In the first half of the season Mancuello didn't perform as expected due to some injuries, playing all of his 12 matches as a starter and scoring 3 goals. As the
2016 Série A started he lost his status of starter, but established himself as of the most important substitutes of the team. On 6 August 2016 Mancuello scored his first
Série A goal in a 1–0 win against
Atlético Paranaense in
Kléber Andrade Stadium, the game-winner goal was scored in a beautiful back heel flick. On 28 August 2016, against
Chapecoense, he substituted
Éverton on the 62nd minute and scored his second
Série A in the injury time, Flamengo won the match 3–1 at
Arena Condá. His third
Série A goal was, once again, a game-winner, this time against
Cruzeiro in a beautiful placed shot in the 87th minute. In his first season at
Flamengo, Mancuello made 36 appearances and scored five goals in all competitions. ==International career==