Simpson has been relegated to a run blocker
Brown can catch the ball, but the Steelers pass protection sux, and with Tennessee's D, Roethlisberger will be on the ground more than he is in the pocket.
Thomas is getting the targets and has decent hands, but Cincinnati is pretty stingy, and I don't know if the rookie can get the ball to him.
Jones is in kinda the same boat as Thomas, with a tough D.. but instead of a rookie QB, he has Fitz throwing to him. I think he's your guy.
None of these guys are gonna light up the field, but but I think Jones has the best chance.