Biggest defensive sleeper is Eddie Moore.. as long as he's healthy. If he can become physically well then I expect him to be a very good LB. Whenever he was in(which hasn't been often), he has looked pretty good. Of course, if he can't stay healthy then he's not gonna be worth anything.
On offense I would say Sammy Morris will do alot more than people are expecting. At least for the 1st 4 games.