After being released, he turned to the Arena Football League (AFL), where he played the 2008 season with the Grand Rapids Rampage and the Philadelphia Soul.

At the end of the 2010 CFL season, Johnson drew interest from several NFL teams, and decided to sign with the New Orleans Saints, where he played from 2011 to 2013.

By the end of his junior year, when the Tigers won the Class 5A title, he was a regular part of the Tigers’ defensive line rotation and earned a starting spot his senior year in 2000–01, when he recorded 90 tackles (25 for a loss) and eight sacks that helped Moss Point get to the playoffs, where they lost the championship game to Starkville.

Johnson earned second-Team NJCAA All-America honors in 2003 at Gulf Coast Community College and was the team's Defensive Line MVP both seasons.

In 2004, Johnson officially transferred to the University of Southern Mississippi, where he played for the Golden Eagles his final 2 seasons with 12 starts.

In his first career game with the Golden Eagles, he helped upset the University of Nebraska on the Cornhuskers' home field in Lincoln, 21–17, in the 2004 season opener.

He arrived at training camp with high expectations, but was hampered by injuries, and then missed the Stamps' season opener on July 1 in order to attend the funeral of his grandfather.

[1] In his CFL debut season, Johnson played in 6 games for Calgary, starting all of them, and was credited with 3.0 sacks and 13 tackles, helping the team advance to the West Division Final before losing to the Saskatchewan Roughriders.

In his second season with the Stampeders, Johnson was part of a defensive unit that tied for first in the league in yards per carry allowed (only 5.5) and that saw him dominate the rivals' offensive linemens for 39 total tackles and four sacks, helping lead Calgary to a 13–5 record and a first-round bye into the league's division final and earning West Division All-star honors for his outstanding work as Calgary dominated the All-Star ballot with 13 selections.

[3] Showing the persistence to jumpstart an NFL career by appearing in different football leagues, Johnson became a significant contributor to the New Orleans defensive line rotation during his tenure with the team.

As a member of the Saints, Johnson appeared in 40 games over three seasons and posted 55 tackles (35 solo), five sacks and a forced fumble.

After recovering from a calf injury suffered in training camp, Johnson appeared in 13 games and recorded 15 tackles (11 solo), one sack and one forced fumble.

On December 28, he was credited with his first career sack when he tackled Vikings' quarterback Christian Ponder for a six-yard loss in the win at Minnesota.

Johnson ranks sixth in the league among interior linemen over the past 2 seasons with 12.0 sacks, with that being the highest total by an undrafted defensive tackle in that span.

After a quiet Week 1, in which Johnson wasn't credited with a single tackle, he contributed with one of the five sacks the Vikings' defensive line had on Aaron Rodgers during the team's 17–14 win over the Green Bay Packers in U.S. Bank Stadium.

In Week 3, Johnson intercepted the first pass of his career when Panthers' Cam Newton threw the ball away on a desperate toss.