IMHO, it would be the O-line. The rumors have Starks, Colone, Foster not in the Steelers plans for 2013, so wouldn't that be a step back letting all those guys go and depending on Adams, Beachum, and Gilbert to fill the void?
Even if that works out who plays if they get injured? John Melecki is the only signed O-lineman on the roster then Legursky still has to be signed.
If they do release those three above, we are going to need replacements in the draft no doubt but which rounds?
Considering the above scenario would you take Warmack if he's there when we pick?