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Nothing lasts for long at running back in a Dynasty league. The career arcs are so short and the value so dependent on situation, there are constant shifts, often major ones. That type of shift is happening at the top right now, with an avalanche of former top-10 running backs falling fast. 

Aaron Jones, Saquon Barkley, and Ezekiel Elliott all began last year inside the top 10 and they're all outside my top 20 in the most recent update. Derrick Henry might not be far behind. And while Alvin Kamara and Dalvin Cook are still in the top 10, they're definitely falling. It would be rare for a running back their age to see a rebound in their value, which means you should be dealing all of these guys unless you're a surefire contender in 2022.

Of course, all these fallers means there must be risers, someone has to be inside the top 10 at running back. Half of those someones are under the age of 25 and will still be at the start of the 2022 season (all ages in the chart below are based on Week 1 of the 2022 season).

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Jonathan Taylor, Najee Harris, and D'Andre Swift have been in the top 10 for most of the past season. Javonte Williams, J.K. Dobbins, and Cam Akers have recently joined them. For Dobbins and Akers, this is more about a reemergence after a lost year due to injury. I was far more concerned about Akers' injury than Dobbins, but the 22-year-old eased a lot of fears with his performance in the Wild Card round. If the Rams continue to win and Akers continues to shine, he could be a lot higher than 12th by the time we get to February.

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Williams is a slightly different story. He had a very good rookie year that was limited by Melvin Gordon, but we saw just how good he could be when Gordon missed Week 13 and Williams exploded for 178 yards against the Kansas City Chiefs. The Broncos will enter 2022 with a new coaching staff, and presumably a new quarterback, which does add some volatility to Williams' projections. But he's not yet at his ceiling either. 

I thought I might have moved Williams up too fast, but a poll on Twitter suggests Dynasty managers prefer him to both D'Andre Swift and Christian McCaffrey. At that valuation I would suggest Williams is more of a sell than a buy, but only if you can get a haul.

Below are my updated Dynasty running back rankings for PPR leagues. Remember, this is a combination of valuations for contenders and rebuilders. If you're clearly in one camp (and you should be) you should adjust these rankings to reflect your current state.