Smith was born in 1947 in Tampa, Florida, and attended Thomas Richard Robinson High School in Tampa. As a junior in 1963, Smith was the star running back on the Robinson Knights high school football team, and led his team to Florida's first-ever state championship football game before losing to the Coral Gables Cavaliers 16–14. He finished his high school career with forty-seven touchdowns, and received all-county, all-state, and Parade magazine high school All-American accolades. In 2007, forty-two years after he graduated from high school, the Florida High School Athletic Association (FHSAA) recognized Smith as one of the "100 Greatest Players of the First 100 Years" of Florida high school football.
Smith graduated from Florida with a bachelor's degree in business administration in 1970, and was inducted into the University of Florida Athletic Hall of Fame as a "Gator Great" in 1983. In a 2006 article series written for The Gainesville Sun, he was recognized as No. 29 among the top 100 Gator players from the first 100 years of Florida football.
Smith was selected in the first round (eighth pick overall) of the 1969 NFL Draft by the Los Angeles Rams, and played for the Rams from 1969 to 1973 and the Washington Redskins in 1974. His rookie year with the Rams was his most productive season: 599 yards rushing and 300 yards receiving. After five seasons with the Rams, he was traded to the Redskins in 1974 as part of coach George Allen's effort to rebuild the Redskins with experienced players. He received few carries with the Redskins, however, accumulating only 149 yards in seven games, with no touchdowns. In his six NFL seasons, Smith gained 2,057 yards rushing on 528 carries for eleven touchdowns; he also had 149 receptions for 1,176 yards receiving and five touchdowns.