The Steelers placed Johnson (hamstring) on injured reserve Monday, Teresa Varley of the team's official site reports.
Johnson was already ruled out for Monday's matchup against the Browns, but he'll now be forced to miss at least four games due to a hamstring injury he suffered during the season opener. Given the Steelers' Week 6 bye, the earliest Johnson could suit up would be Week 7 versus the Rams. In Johnson's absence, Calvin Austin and Allen Robinson should see more snaps behind George Pickens.