A different era for sure. I can make this short and simple.
I believe the current common career average for running backs in the NFL is around 3 years. That’s just the modern statistics.
Barry Sanders played 10 seasons.
It just makes me chuckle, because Barry gave us a whole decade… and it wasn’t good enough.
All positions except QB have seen a steady decline in average career length because players abuse their bodies so much more than in the past with the amount of excess training they do to push their bodies past their genetic limits.
The average career length for RBs in the 90s was around 2.8 years and now its around 2.6. I think there is a perception that they played longer because of guys like Barry and Emmitt Smith having longer careers but they were exceptions. I also think there was more of an incentive then to play longer because RBs were paid much more (relative to the time period) then they are now.