It appears that Moreno has secured the lead back role, while Miller's lack of production has set him as the change of pace back. (Miami Herald)
Fantasy Impact
While Miller is capable of hitting home runs he needs running land that the O-line hasn't be able to give him. The value of the Dolphins backfield has lowered as the two will split carries with Moreno as the lead. Miller shouldn't be anything but a late round pick now with Moreno fully health.