I don't know all the exact dates, and my memory is a little thin, but as I understand it, as the preseason rolls on, trades and signings are made, players come and go and salary cap plays a continual role in moving, keeping, and cutting players. Along the way there are usually a few pretty good RBs cut for one reason or another.
Couldn't the Rams just wait until a good RB becomes available and make a move to get him? Why make a trade now when there will be a better quality guy, or the same guy, available for cheaper in a month or so?
Penny or Jones sound good to me.