Dennis Northcutt replaced Johnson in Detroit's lineup Sunday.
Stafford missed two games with an injured right knee. He was able to rest last week because Detroit had a bye.
The No. 1 pick in the NFL draft threw three touchdowns and six interceptions in his first four games. He helped the Lions win in Week 3 win against Washington to end their 19-game losing streak.
Johnson did not play in the Lions' previous game, a 26-0 loss at Green Bay, after injuring his right knee Oct. 11 against the Steelers. He has 22 receptions for 325 yards receiving and a TD this year. Last season, Johnson had 12 TD receptions.
The Rams were without starting right guard Richie Incognito, as expected. He injured his right foot last week when St. Louis lost to Indianapolis and extended its losing streak to 17. Adam Goldberg moved from right tackle to guard, putting Jason Smith back in the lineup. Smith started the first two games of the season. The No. 2 pick in the draft then missed two games with an injured left knee and was a backup in the previous three games.
St. Louis had David Vobora at linebacker in place of Larry Grant. Vobora practiced Wednesday for the first time since a four-game suspension for violating the NFL's substance abuse policy. The second-year player has said he plans to file a lawsuit, claiming he took supplements that he checked on through the NFL hot line.