 After acquiring Valenzuela in the summer of 1979, the Dodgers assigned him to the Lodi Dodgers of the High-A level California League where he posted a 1–2 record and a 1.13 earned run average (ERA) in limited action.The Dodgers felt that Valenzuela needed to learn to throw an off-speed pitch, so they had Dodgers pitcher Bobby Castillo teach him to throw the screwball before the 1980 season.In 1980 Valenzuela was promoted to the Double-A level San Antonio Dodgers.