My RB Depth is almost destroyed!

I am in quite a pickle. My main RB depth chart for my ten team full PPR super flex league is composed of:
RB1 - Chris Carson
Was RB2 - Tevin Coleman
My two other backs are David Montgomery and Devin Singletary.

I need help deciding who to start as my RB2? Thanks for the help.

P.s. I am in the works of trying to negotiate for Josh Jacobs, but if I don’t get him who do I start?

I’d start Singletary based on matchup and workload.


Much appreciated!