Riley suffered a high-ankle sprain in Sunday's loss to the Browns, according to head coach Mike Tomlin, Mike DeFabo of The Athletic reports.
Riley headed to the locker room after suffering the injury and was unable to return to the contest. His likely absence for the week ahead will be another blow for Pittsburgh's secondary, which has lost Keanu Neal (ribs) to injured reserve and remains without Minkah Fitzpatrick (hamstring) for the time being.