His abbreviated MLB service notwithstanding, Valenzuela played 20 years in professional baseball (1952–71), with the last decade spent exclusively in the Double-AMexican League and lower-classification Mexican minor leagues. He began his pro career with the Bisbee-Douglas Copper Kings, an unaffiliated team in the Class C Arizona–Texas League, then was drafted into the Cardinal organization in 1955. After hitting .314 and .286 in consecutive seasons with the Double-A Houston Buffaloes in 1956–57, he received early- and late-season auditions with the 1958 Redbirds, spending the bulk of that year with Triple-A Omaha. He singled in his first MLB at bat off Johnny Podres of the Los Angeles Dodgers on April 27,[2] but overall collected only three hits in 14 at bats with a base on balls during his lone big-league campaign. At the close of the 1958 season, Valenzuela was traded to the San Francisco Giants in a five-player transaction that netted the Cardinals right-handed pitcherErnie Broglio.
Valenzuela owed his nickname, "Papelero", because he worked as a paperboy; he also worked as batboy for the Cañeros de Los Mochis before turning into a professional baseball player.[3]
After his playing retirement, he became manager of the Alijadores de Tampico in the Mexican League, winning one title in 1975.
