Top 2016 NFL Free Agent Running Backs

Bryan Altman, CBS Local Sports
In terms of volatility, the running back position in the NFL has no equal. Of course, turnover in the NFL and other sports leagues is at an all-time high, but still, no one position experiences as much change on a year-to-year basis as the running back position. 
If you take a look at almost every NFL team’s depth chart today and look back between three to five years, you’ll almost certainly see a different running back’s name atop that list.