The main points where:
Nobody wants to invest in running backs long-term, and even when they do, they want to protect those investments. As teams pass more, and as teams split carries more, nobody is being asked to shoulder the load 25 times every game. It's a logical strategic shift, but it also signals a change in the way we view players. Running backs were once almost full and equal partners in the backfield with the quarterbacks. Now, in many cases, they're becoming expendable bit players, the "thunder and lightning" systems -- see the Bengals adding Hill despite Bernard's stellar rookie year -- relying on multiple backs combining to create the same impact of one back in past years.
But in only a few years, that changed, following the trends on the field. Aside from obvious stars like Adrian Peterson and LeSean McCoy, committee approaches and pass-first offenses have taken hold, rendering running backs almost interchangeable in some systems. It's had a similar impact in the actual NFL draft, where the possibility of striking gold in the later rounds or after the fact -- see Terrell Davis and Arian Foster, among others -- combined with the
short shelf life of the position makes spending a first-round pick on one a risky proposition. By taking a running back in the first round, an NFL team is betting that he can be a bell-cow back who's not going to wear down quickly. There are very few players, if any, who safely meet those criteria.
