Mike Adams sprained his ankle in the Steelers' 20-14 loss at Cleveland in Week 12, and Marcus Gilbert was placed on injured-reserve Monday.
Beachum wasn't thought to have much of a chance at even making the team after he was drafted out of SMU. He was kept in favor of veteran Trai Essex, and has been up and down in activation status this season.
Adams was beaten frequently by Ravens LOLB Paul Kruger in Baltimore's Week 11 win over the Steelers, leaving Pittsburgh in a precarious situation. With Adams out, it seems likely the Steelers will provide Beachum help with tight ends and running backs, and that's with an increasingly healthy Terrell Suggs on the other side of the line.
The Steelers (6-5) are the AFC's sixth seed heading into this game. Baltimore can clinch the division with a victory over Pittsburgh - a win would give them 16 straight at home, their fourth straight win over the Steelers and their second straight AFC North title.