Johnson attended Northeastern Oklahoma A&M College, before transferring to Northern Illinois University as a junior. At Northern Illinois, he played for the Northern Illinois Huskies football team in 1992 and 1993. As a senior in 1993, Johnson was the leading college rusher with 1,976 yards on 327 carries for an average of 179.6 yards per game. Johnson finished sixth in the 1993 Heisman Trophy voting race, with five first-place votes. He played only two years for the Huskies, but his total yards mark of 3,314 still places him fifth on the team's all-time rushing list.
The Green Bay Packers selected Johnson in the third round (84th pick overall) of the 1994 NFL Draft, and he played for the Packers in 1994 and 1995). From 1995 to 1997, he was a member of the Arizona Cardinals. In Johnson's career-best game, he rushed for 214 yards on 21 carries for the Cardinals versus the New Orleans Saints on September 22, 1996. His career was interrupted by lymphoma cancer in 1998. He managed to make a comeback and subsequently started for the New York Giants in 1999. His football career ended playing in the XFL for the Chicago Enforcers.