If he does rotate often I don't think "playing them off of each other" comes into play... not intentionally nor in the minds of the RB's themselves...... not with our 2 starting RB's inactive.... and both going inactive in the same week! That's a big problem.... thus "any" answer will be viewed as a stress on success and the method used reflective of that and not an introduced RB competition.
As for why I don't like it either.... what you said.... doesn't allow for any RB to get into a rhythm. I doubt the talent level difference between our RB actives this coming week is much more than miniscule... (not saying they aren't talented, just very even in talent).
