A Top-10 running back is a difference maker because not only do they score among the highest fantasy points of any position, but they do so with greater consistency. The position is always gives up most of the first round in any fantasy draft. Likely the second as well.
See also:
Top-10 Repeatability: Quarterbacks
Top-10 Repeatability: Tight Ends
Top-10 Repeatability: Wide Receivers
Below are the running backs that produced a Top-10 finish in any of the past five seasons, and what they did in the other years. This shows the volatility of the position and how rarely backs actually return to the Top-10 the following season, despite the fact we all draft like they are going to repeat.