He played college football for the Ohio State Buckeyes and was selected by the Bengals in the second round of the 1977 NFL draft.

Born in Fort Valley, Georgia and raised by his great-grandparents, Johnson attended Peach County High School for three years where he played football.

Although two-time Heisman Trophy winner Archie Griffin got most of the carries at tailback from 1972 to 1975, the Ohio State fullbacks still got the ball frequently and were expected to be major contributors, particularly in short-yardage situations.

In 2000, Johnson was selected for the Buckeyes All-Century Team, and he was inducted into the Ohio State University Athletics Hall of Fame in 2007, presented during halftime of the Akron game on September 8.

In the AFC title game (known in NFL lore as the Freezer Bowl), Johnson rushed for 80 yards and a touchdown, while also catching a 14-yard reception as the team defeated the high-scoring San Diego Chargers 27–7 to earn their first Super Bowl appearance.

[4] In 1983, Johnson and another Bengals player testified in exchange for immunity from prosecution that they had purchased cocaine from a Cincinnati plumber, and he was suspended by the NFL for four games.