It seems to me that the RB3 always ends up mattering. (Bit of trivia here: per Gemini, no team in the modern NFL era has ever gone a full season with only two RBs getting carries.) But I agree, I don’t think Jennings was in line for the job.
I can't see sitting Stevenson and Henderson for Larison or Miller...however Gibson, Jennings and Johnson had some carries. Probably garbage time but still...they has some.