Gilbert (back) was placed on injured reserve Tuesday, Teresa Varley of Steelers.com reports.
Gilbert, who was selected by the Steelers in the sixth round of the 2019 NFL Draft, was bothered by a nagging back injury in recent weeks. The issue forced him to miss a Week 8 win over the Dolphins, though he was able to return and log 15 snaps on special teams Sunday. In a corresponding roster move, Pittsburgh promoted fellow inside linebacker Robert Spillane from the practice squad with Gilbert on his way to IR.