Born in Armstrong, Santa Fe Province, Delfo played football as a youth, but decided to turn to athletics after Juan Carlos Zabala's triumph at the 1932 Summer Olympics.

He moved to Buenos Aires in 1938 and began training in San Lorenzo de Almagro under Francisco Mura.

Delfo served in the army during the World War II where he met Juan Perón.

Cabrera also participated in the 1952 Summer Olympics and was the flag bearer for Argentina at the opening ceremony; he finished in sixth place in the marathon, which was won by Emil Zátopek.

Cabrera ended his athletics career after finishing sixth at the 1954 Boston Marathon.