@kearly
The only way Brooks can make the roster is if he balls out, and they put Prosise on IR. They won't carry 5 runningbacks, I'm sure they will be debating whether they even carry a fullback, and instead carry an extra TE.
1 Rawls
2 Michael
3 Collins
4 Prosise
-------------------- 53 Man cutoff line
5 FB???
6 Brooks
So early in the season they decide to carry Prosise on the 53, but he is not ready to play due to lack of reps. Rawls is the starter, but not fully recovered, so he will share carries with C-Mike. Leaving Collins who can carve out a nice role as a 3rd down back early in the season.(Similarly to Turbin who was a bigger 3rd down back.) Collins isn't the permanent solution, but for the early part of the season it is looking like it's playing out this way.
Collins lack of catches in college doesn't bother me because in his limited opportunities, he looked natural doing it.
Turbin in pads was/is slower than Alex Collins in pads. Collins has excellent burst, and light feet. Turbin played like he had cement galoshes on his feet.
All of this is moot of course if Prosise can get on the field, and earn the role that has been earmarked for him from the beginning.