No position changes as fast in Dynasty as the running back position, and the 2021 season has signaled a massive shift that is to come.
Just looking at the rankings below you'll see Christian McCaffrey, Dalvin Cook, Ezekiel Elliott, Derrick Henry, and Aaron Jones have all fallen, with all but McCaffrey exiting the top 10. And this is just the beginning. Henry is already 27 years old. Jones turns 27 on Dec. 2, and both Cook and Elliott will turn 27 before next season.
Why is 27 significant? It's historically been the last year you can count on elite Fantasy production from a running back. Sure, there are a few exceptions to the rule, but there are far more backs who have completely fallen off the age cliff at age 28 or 29.
The thing with the backs who have already fallen is that they've suffered injuries, or seen their play fall off. The fact that you can't use McCaffrey or Henry the rest of the season does hurt their Dynasty value, even if it doesn't to rebuilding teams. That's because rebuilding teams don't have any business acquiring running backs at this stage of their careers.
All of this points to the two 26-year-old backs who are in the top five, Alvin Kamara and Austin Ekeler. Should Fantasy managers be wary of them? If you aren't playing for a title this season, you absolutely should. Because entering next year they'll be clear sells for all but the true contenders. But with the current state of the running back position and their current roles, it's hard to rank them any lower.
Just know that as much as 2021 has altered the running back rankings, 2022 figures to be worse. Or better if you're someone like J.K. Dobbins, Javonte Williams, Michael Carter, or Elijah Mitchell. They may all be in the top 12 a year from now.