With RBBC now it's a matter of pay. They aren't going to pay them to be #1 backs when they can't stay healthy, but they can pair them with backs and run two back systems and it will be fine.
McFadden is in the last year of his contract, and I'm not sure if he'll be back or not either way unless he just blows up.
Mathews has two more years on his contract, and barring an absolutely horrible season I expect him to play both of those.
Let's not act like a 6th round RB is really supposed to be a message to McFadden when they had no depth.