Castonzo (knee/ankle) has been ruled out ahead of Sunday afternoon's game against the Steelers.
Castonzo appeared to be trending in the right direction upon logging a limited session Wednesday, but a reversal to no participation Thursday seemingly doomed the 32-year-old's Week 16 status. He was able to power through his knee issue to get the start last Sunday versus Houston, but now Chaz Green is expected to man the left tackle spot against Pittburgh's injury-depleted front seven.