In its first year in the league, the Leones won 47 games and lost 32, with one tie, and finished in second place to the defending champion Tecolotes.

[2][3] After the 1969 season, filmmaker Manuel Barbachano Ponce, moved the Pericos de Puebla franchise to Mérida, renaming it the Leones.

The franchise remained in Mérida for five seasons and then moved to Villahermosa, Tabasco, when Ariel "Picho" Magaña Carrillo purchased the team.

[4] On 16 March 1979, the Leones officially returned to the Mexican League when they opened the season at the Cafeteros de Córdoba and lost 10–4.

Valenzuela had a win–loss record of 10–12 with an earned run average (ERA) of 2.42 and allowed only 70 walks while striking out 141 batters in 181 innings, catching the attention of the Los Angeles Dodgers with whom he would play from 1980 to 1990.