I'm not sure what 2013 has to do with anything. His good year was two years ago (2015) and last year he was TE5 over the 7 game stretch he played, with a pace of 64-880-11.
These guy's value is always at its lowest right after their injury when everyone is upset about it. I'd rather hold Eifert and see what happens then have a half-season of mid/back-end TE1 production from Walker, who is currently sandwiched right in the middle of Charles Clay, Cameron Brate, Ed Dickson, and Jesse James in TE scoring.
Yes back injuries are scary but the only other TE to go through this many back issues is the consensus #1 dynasty TE right now so it's not necessarily a career ender.