Smith-Schuster aggravated his left knee injury at Thursday's practice and isn't expected to play Sunday against the Bills, Adam Schefter of ESPN reports.
The 23-year-old appeared on track to return from the three-game absence after practicing as a full participant Wednesday, but he was downgraded to limited participation Thursday after suffering the setback. Smith-Schuster's status will receive additional clarity when the Steelers release their final injury report of Week 15 on Friday. James Washington and Diontae Johnson would be in store for boosts in targets in the event the team's top wideout remains out.