He didn't show top 15 upside. He achieved top 11 actual performance.
Why do you think it's not sustainable? His 4.4 yards per carry are slightly above average. His 10.2 yards per catch were barely top 5 RB, and guys like AP, Gore, Ekeler, and Drake were above/right at that number. His touches/TD were slightly above average at 21.25, so he wasn't TD dependent - Conner, Marlon Mack, Chubb, Coleman, Lindsey territory. I don't see anything he couldn't do every single year of his career.
I don't mean to beat you up on this, and I won't draw the conversation out any more, but Cohen is one of my favorite players at his current price/perception in PPR leagues.
I am not trying to convince you not to like cohen, but i'll address a couple of these points.
Top 11 actual performance is not that great.
First, being 11th in end of numbers just means you stayed healthy. Cohen scored more than Melvin Gordon, but it's not close between them.
Second, a lot of guys who are lower in ppg - like Nick Chubb and Derrick Henry - were more valuable when they "started" than in simple games played.
Third. some of the guys behind him iast year include Peterson or ther philly running backs. Derrius Guice looks may be a better ppr back than Peterson, and Howard is almost certainly better than the guys philly rolled out last year.
Fourth, some situations - like the kc running back - are much higher upside than cohen. Not only did both Hunt and Williams outscore Cohen while they were starting, but the upside of the situation is clearly higher than Cohen.
Lastly, those little ppr backs don't repeat as often as you'd like to think. He's 181 lbs. Guys like Duke Johnson, Buck Allen, Darren Sproles, Danny Woodhead, Theo Riddick, Chris Thompson... some repeat year after year, some don't.
You can argue that cohen is different and i won't disagree. You can argue each point or all of the points, i won't disagree.
The real issue - imo - is that you should have more than 11 guys projected to meet or exceed rb11 numbers.
I think it's obvious that you'd take Barkley Elliott McCaffrey Kamara Gurley Gordon Chubb Conner DJ and Mixon ahead of him. That's 10 guys. So i don't see how you could project him to improve on rb11.
Then there's Guice, Fournette Carson, Aaron Jones, Sony Michel, James White, Lindsey, Henry, Drake and Ingram. That's before you add in a couple rookies.
There's also guys you might take ahead of him that will solidify after the NFL draft. Like damien williams or the top kc rb - it's easy to downplay them now but by September somebody will be the number one and i'll take them over Cohen for sure.
My point is that without even digging into my thoughts on cohen specifically, i can already see myself taking a lot of guys ahead of him. Not all of the guys I listed, but a lot of them. And some more will emerge. Because i like the upside of 3 down backs a lot better than 3rd down backs. I simply don't see him as a threat to be a top 5 back, and i can see a lot of those other guys doing it.