Due to his skill to play basketball, Montenegro has been compared with talented players such as Puerto Rican José Piculín Ortiz, Brazilian Oscar Schmidt or Spanish Fernando Martín Espina.

Olimpo reached the finals of the LNB] that year although the team was defeated by Ferro Carril Oeste with Miguel Cortijo as its star player.

He later received a basketball scholarship to play at Louisiana State University of the NCAA, but after suffering a broken left ankle one day before the season started, he chose to end his college career because he needed to support his family.

Although Montenegro did not keep in mind coming back to Argentina, some disciplinary affairs and personal problems with the managers caused a premature return to his native country.

The matches of the 1990–91 season disputed for Estudiantes are considered the best Montenegro's performances of his career, leading a team where also played other prominent players such as Juan Espil, Javier Maretto and José Luis Gil.

Since then, Montenegro's partners, rivals and even journalists began to nickname him "El Loco" ("The Crazy", in Spanish), due his strange behaviour inside and outside the courts.

Nevertheless, he soon returned to Argentina again to play the 1993–94 season for GEPU San Luis, and the next (1994–95) for Gimnasia y Esgrima de Comodoro Rivadavia where he achieved his best record in rebounds (8.8).

In 1995–96, Montenegro returned to Estudiantes and then he signed with Valle Inferior, a team from Viedma, Río Negro, playing only 11 matches and finishing that year in Venezuela Gauiqueries.

In February 2012, two years after his retirement, Montenegro signed with Del Progreso, a club from Río Negro Province, to play a new season of Torneo Federal, the third division of Argentine basketball league system.

Manu is an extraordinary athlete and a very good player who quickly learnt all he needed to learn, but Ginóbili never was as talented as Cabrera, Pichi Campana or I were.