Maurice Jones-Drew last year seemed to define what an NFL workhorse running back should look like. In a season when the Jacksonville playbook was essentially just a picture book with MJD's face on every page, he ran the ball 343 times for 1,606 yards. No other NFL runner was within 40 carries of MJD (two games' worth). No other Jacksonville runner topped 130 yards.
Yet, if you took every running back from the past 25 years, put them together in a group and ranked them based on most carries in a season, not one runner the past five years in the NFL would even crack the top 25. MJD's quintessential workhorse season, the one that has him waiting for a new contract? It ranks No. 50.
In reality, the traditional "bell cow" back by the old standards doesn't exist. Larry Johnson might have been the last of its kind. He carried the ball 416 times in 2006 at his physical peak and, in a good lesson of what 416 carries in 16 games can mean, rushed the ball a little more than 500 times the next five years the rest of his career. Whether NFL teams learned the lesson from Johnson's example or the life teachings of "Varsity Blues" ("It's not worth it"), the don't-take-him-out approach to running backs is hard to find in the modern game.
Most teams diversify by design or necessity, so instead of ranking running backs, let's rank the manner in which groups are deployed, the best backfields in terms of overall efficiency and productivity entering 2012. (So don't cite an incredible 2010 for one guy, or forget about injuries for another.) For this exercise, I've excluded the running quarterback as a part of the mix, mainly because in large part, the "running QB" isn't by design.