I think Carson is a safe play this week. Sure, he has a shorter leash than some of his counterparts out there, bit at thia point i think you have to start him.
IMO his fall from #1, if it occurs, will be slow. This isnt NE where a guy goes i to the dog house on 1 carry never to be seen from again. Carson didnt suddenly just start with fumble issues. He had them last year yet Seattle stuck with him.
Penny looks better than last year, but weve only seen him in small doses. In larger doses he may be less effective, and he may not be mentally (or physically) ready for larger doses.
That all being said, I think the hopes of Carson being a top 10 or more RB are a little misguided. I think he will have RB2 value rest of season unless Penny makes significant strides and Carson continues to put the ball on the ground.
Could be a sell high situation after this week if you can find someone who still values him as a RB1
Worst case, IMO, he is a RB1a or 1b in one of the most run heavy offenses.