"Stevie has missed two days," coach Doug Marrone said. "I don't feel as good about him being able to play, but I can't officially rule him out just yet."
Rookie receiver Robert Woods (ankle) has already been ruled out for Sunday's game, so if Johnson is unable to play, the Bills will be without their top two receivers.
Meanwhile, safety Da'Norris Searcy returned to practice Thursday and is expected to play Sunday.
"Searcy looked good," Marrone said. "No issues there, and unless he has a setback during the week, he should be in good shape."