McDuffie (back) did not participate at practice Thursday, Adam Caplan of SiriusXM NFL Radio reports.
McDuffie was estimated as a non-participant on the Rams' injury report Wednesday after being sidelined in Week 9 with a back injury, and his condition doesn't seem to have improved as of Thursday. Unless he's able to practice in some capacity Friday, there's a good chance he'll be out again Sunday at Arizona.