So looking at the available guys, I think their are 4 defensemen available for a bottom pairing role, that wouldn't be complete blackholes. All have a few holes in their games, but thats why they are third pairing guys.
Anton Volchenkov-Slow as heck and zero offense, but hits like a truck and fairly solid positionally. Good on the PK.
Jaime McBaine-Was terrible last year, but had 3 or 4 solid years before that in Carolina. I think the carolina years were he was a solid 2nd/3rd pairing guy is more indicitive of his skill than one year on a Dumpster fire team.
Paul Ranger- Head Case that may never want to move out of Toronto, but scores 5v5 points at an extremely good rate. Played rediculous minutes last year(40% o zone starts).
Rapheal Diaz- Had great numbers playing for NYR and Vancouver, but always been a bit up and down.
I'd look into those 4 guys, and see if they can be had cheap and short term. If none bite, stand pat.