He was productive in 2011 and 2013, and not effective in 2012 and 2014. IIRC, both 2012 and 2014, he played injured because CJ was out, and we had thin depth at the position.
This year we *should* have at least 3, if not 4, good runners on the team... it's just bad luck they're all banged up at the moment. Anyways, my point is, if FredEx is injured this year, most likely he won't have to rush back and play before healing, not to mention he likely won't get the majority of the carries, so should stay fairly fresh as a depth guy.
That all being said, if the coaches feel Brown, Karlos, and Boobie are more valuable to keep, then I'll understand. FredEx is old. He does a lot of the little things well, and he churns out yards when there are none, but it's hard to argue against father time.