From the official site:
The Bears haven't had a defensive starter sit out a single game with an injury this season, but they could be missing both of their safeties Sunday in Pittsburgh.
While rookie free safety Chris Harris is sidelined with a sprained knee, veteran strong safety Mike Brown was added to the injury report as questionable after missing practice Friday with a calf injury sustained during Thursday's workout in the Walter Payton Center.
Looks like Mike Green might get his audition for some other team next year after all.