Leaks was an all-state running back and linebacker for Brenham in 1969 and 1970. During his junior and senior seasons he rushed for 3,688 yards, 55 touchdowns and led Brenham to a 22-2-1 record. The Cubs won two district championships and beat Bridge City, 40-12, in the 1969 bidistrict playoffs. Brenham then advanced to the quarterfinals but lost to West Columbia on penetrations. As a senior, Leaks made the PARADE High School All-America team and played in the 1971 THSCA All-Star Game. He later played at the University of Texas from 1972-1974 and made All-SWC running back in 1972 and 1973. His junior season he was a consensus All-America selection. Leaks rushed for 2,923 yards during his career at Texas, including a record 342 against SMU in 1973. He played in the NFL with the Baltimore Colts from 1975-1979 and the Buffalo Bills from 1980-1983.