Let me say this one thing about Peterson and the "bigger risks" theory. Running backs do have a short lifespan in the NFL, and Peterson could be at the point where he hits the wall, but I do think you have to consider the fact that he hasn't shown himself to be the normal running back.
Emmitt Smith played 11 seasons before he essentially hit the wall (even though he had one more 1,000-yard season). At what point in time was it wishful thinking in terms of how he would perform?
I believe it's wishful thinking to believe that McFadden is going to be a 4.0-plus back after three years under 3.5 because the evidence is against him.
Peterson's numbers indicate that he might be much more like Emmitt than like McFadden. In the sixth year of his career, he had his best season, topping out at 6.0 per carry. Even in his last full year, he averaged 4.5. There's no real indication of decline looking at his career numbers unless you count the one game he played in last year.
There is more reason to believe he would be able to keep up what he's been doing throughout his career rather than suddenly dropping off. Could it happen? Of course. But it seems about as likely as Emmitt dropping off suddenly from the player he had shown himself to be.
