Again, Bush is the starter, not a "role player." You're missing the point entirely it seems. Dunbar can run and well. He's just not a great pass blocker. However, if he's not your starting RB, why should that be bothersome? Especially with this OL. He won't be sitting in pass protection often and even if he is used on screens more than runs, it still lets you fake the screen and or run and makes the defense unable to thwart all of it's attention on other play makers. I've a feeling the way that all 4 backs looked behind the starting 5 that, you could put a pee wee football RB in and still average 4 yards a carry. I'm not worried in the slightest about Williams being released. I get your point, Dunbar is not Reggie Bush. Which is why Murray is the starter. Randle is the just in case Murray goes down and Dunbar is your change of speed, decoy, what have you.