RB1: Knowshon Moreno
RB2: Lamar Miller
RB3: Mike Gillislee
RB4: Marcus Thigpen
Daniel Thomas hasn't been released by the Dolphins yet, but as his non-placement on our projected depth chart shows, I'm going to speculate that he will be.
I already like Knowshon Moreno's attitude coming into Miami. While most free-agent signings who started with their previous team would likely expect to start upon signing their name on the dotted line, Moreno expects to compete, per Adam Beasley of the Miami Herald:
[I’m] definitely competing. Compete and the best man will win. We’ll learn from each other. And the same time, we’ll go out there and compete and do what we have to to help this team win.
That's the attitude of a winning culture, and will not only serve Moreno well, but will also help out Lamar Miller. You will see the two backs splitting carries next season, with Moreno more likely to be in the game on passing downs and in short-yardage situations, which Miami struggled with last season.
Miami is still likely to sign a running back, as they only signed Moreno to a one-year, $3 million deal. What the signing does do for the Dolphins is it allows them to wait until the middle rounds to draft a back instead of spending a second or third-round pick on a Carlos Hyde or Tre Mason.