The Lions placed Harper (ankle) on injured reserve Saturday.
Harper has not been able to practice since sustaining an ankle injury during the Lions' Week 2 loss to the Bills. The safety departing for IR leaves the Lions' secondary dangerously low on defensive backs, now without Harper, Avonte Maddox (foot), Brian Branch (Achilles) and Kerby Joseph (knee). The Lions have elevated Jalen Mills from the practice squad to start at Strong Safety in Sunday's game against the Jets.