Johnson pulled up at the end of a route and fell to the turf untouched. He hopped off the field and went to the bench. He sat with his head in his hands as trainers checked him out.
He got up after a few minutes and walked gingerly to the locker room. The team says his return is questionable.
It was his second game back since missing six games after surgery to repair an injury to his right hamstring.
He had four catches for 97 yards Sunday.