The Bears placed Billings (pectoral) on injured reserve Thursday, Scott Bair of Marquee Sports Network reports.
Billings suffered a pectoral injury in the Bears' Week 9 loss to the Cardinals and underwent successful surgery earlier Thursday, according to Courtney Cronin of ESPN.com. The 29-year-old defensive tackle is without a clear timeline for a return to game action, but he'll have to miss at least four contests after being placed on IR.