I'm not sure I totally agree with the RB assessment, but then again I may be missing what you are trying to say. If your contention is that PLAYER Y needed PLAYER X on his own team to fail or get hurt to have fantasy value, then I would say that wasn't really the case for a number of backs. Guys in that bin include Ryan Mathews, Reggie Bush, Beanie Wells, Marshawn Lynch, Fred Jackson, etc.
That is my point, although there are exceptions. Guys like Lynch and Jackson got major bumps due to their team situation, Lycnh also losing weight. But, guys like Murray, Spiller, Sproles, K. Smith even Reggie Bush (who wasn't projected to be a workhorse), benefitted because other risky backs didn't pan out.So, rather than there being a major influx of available RBs during the season, there is simply a shuffle. Kevin Smith was a nice find, but only because Best went down. Spiller because Jackson went down. Willis because Moreno was a bust, then wen't down. The shuffle is a raffle - every owner in the league has a shot at these guys. But, the ones most hurt by it, are the ones that waited to draft a RB. They drafted guys like Best, Felix, Ingram, Thomas et cetera. So, suggesting that this shuffle is a positive to those who waited to draft a RB is false, in my opinion. In most cases, those owners are simply trying find band-aids - lesser options than those they drafted in the first place. The handcuff effect/benefit is further evident here: Nobody drafted Toby Gerhart earlier than his handcuff value dictated, because he simply wasn't going to beat AP out. People did draft McGahee earlier, because he had a shot to beat out Moreno. People did draft Pierre Thomas earlier, because Ingram was a question mark and in a RBBC. So, waiting on a RB makes it harder to get the handcuff/other parts of the RBBC, because they have more value. Again - those that lost Moreno, likely went back into the "shufffle", to find band-aids. Those that lost AP, had Gerhart.