Thought I would throw in my 2 cents. BTW, I have a personal rule that I don't bend over for anything that is worth less than 25 cents, so that means my opinion isn't worth getting bent out of shape.
Leggett should give B-Back a try. He should also give A-Back a try. If he excels at one position but not the other, he should play where he excels. If he excels at both positions, he should play where it helps the team the most.
Yes, we do lose our starting B-Back for 2015, but we will also lose Days, Hill, Perkins, Zenon, & Bostic at A-Back. Not only starters, but a lot of depth at A-Back. I'm not sure I can say which position will have the most need for 2015.
I sure hope the coaches are pointing out the depth chart to stud running back recruits. The opportunity will be there for an excellent freshman running back to make his mark in 2015, whether it be at B-back or A-back.
Regarding Days, I think he stays put at A-back. He is a starter there and I doubt that he would start over Laskey at B-back.
Regarding B-backs in general, I think it is probably relates more closely to running backs in other systems than some posts in this thread would lead me to believe. I also think that the A-back and B-back positions are more similar than some posts here would lead me to believe. It is still running with the football.
Regarding size, I don't think it matters. I think it is the results that matter.