Belén gave his first steps as a footballer in Newell's Old Boys, where he played from 1951 to 1956. Nevertheless, he is mostly known for his tenure at Racing Club de Avellaneda, where he played 174 matches scoring 42 goals. Belén's highlights with Newell were two goals v Rosario Central that helped his team to win both matches. Some of his teammates there were Jorge Griffa and José Yudica.[2]
Belén was part of the first tours that teams outside Buenos Aires went to Europe, playing with Newell's in some friendly matches in the Netherlands and Luxembourg. After he suffered tuberculosis during one of those tours, Belén had to leave football for one year, but as his performances deceased due to the illness, Newell's executives decided to cancel his contract. As a result, he moved to Buenos Aires to play for Racing Club de Avellaneda.[2]
Although Belén started playing as a midfielder, he gained recognition as a left-winger, after Racing Club coach José Della Torre moved him to that position, although he denied playing as a winger at the beginning. Because of his performance at the 1959 South American Championship, Belén was considered the best left-winger in the competition.[3]
