Here is my thought on the topic.. why not Starks.
This is with the premise that we are marching forward with the stable we have.
Starks has not been a model of durability in college nor the pros.. but he has playoff experience under his belt. So he provides value as the playoff push and run draw closer, hence his still being on the roster.
But I think the Packers are trying to protect him somewhat so he is fresh towards the end of the year and in the push. Benson is a maybe on his return at best, that injury is just that unpredictable. Increasing Starks value in the postseason.
So the Packers are feeding Green the ball currently with hopes that experience leads to performance improvement. Green was a one cut hole reading back in college, to write his vision off already is premature in my eyes. He isn't going to improve on the sidelines.. so feeding him the rock now is going to tell the Packers what they have in him.
My opinion as runners, I like Green better as a pure runner, he runs behind his pads and low. Starks on the other hand is more vertical, and although he runs with some power, he takes a beating in the process.
Summary, I think the Packers are better off with Green as option 1 and Starks as the overflow for the above mention reasons at this point. Starks will get to knock the rust off and yet is protected as a back can be in terms of injury risks. Benson's progress will then dictate the roles moving forward, if he comes back, Starks will move more towards the feature back and Green will overtake the role the serves him and the Packers best.. 3rd down and change of pace.
"The oranges are dry; the apples are mealy; and the papayas... I don't know what's going on with the papayas!"