Jeff Leonard was a product of the heralded Dodgers' farm system of the 1970s, but was traded to the Astros in 1978 where he batted .385 in an eight-game audition. In 1979, he batted .290 and stole 23 bases as The Sporting News NL Rookie of the Year, however, he hit no homers and drew few walks.

Houston traded him to the Giants in 1981, where he earned the nickname "Hac-Man" although some teammates noted his dour expression and dubbed him "Penitentiary Face". He became a two-time All-Star and helped the Giants to the division title in 1987.