Ramon Foster, a guy who might know a little something about blocking schemes, addressed this. He said that if you watch the OL when Najee runs, they are usually attempting zone blocking and that this requires Najee to be patient and not attack until a hole opens up. The problem is that oftentimes there is no hole that opens and Najee is forced to kinda freelance. And, that is not his strength.
Warren on the other hand gets calls that require the OL to block specific players rather than areas. The OL is more adept at that (but still subpar). This allows Warren to hit holes faster.
Seems to me they are calling plays and blocking them in the exact reverse way that they should given the players’ skill sets.