Johnson injured his knee during Thursday's practice, Nick Underhill of The Advocate reports.
Johnson underwent an MRI on Thursday after injuring his knee and the results of that haven't yet been released, leaving him without a timetable for return. Since joining the Saints in 2014, the fullback has played in 17 games, totaling just 31 yards rushing and one touchdown. A bulk of his snaps come on special teams, where he played 39 percent of the teams snaps last year. His lack of offensive production renders him irrelevant in nearly all fantasy formats this season.