With us, 4-6 weeks is the type of injury that always inevitably becomes 8-10 weeks. Unless it's McShane, in which case he's back in time for the weekend whatever.
And also playing Elmo as RB in a 4 in an away game is not a good idea. Rosenior, yes. So I agree stick to 3-5-2 and McShane or Bruce to come in. My personal choice would be McShane if he's still not pissed off with being out the matchday 16 in recent games.
You'd find a place for Bruce or McShane ahead of a place for someone like Ramirez or Ben Arfa? You think Elmo or Robbo, who would still be able to bomb forward, offer as much attacking threat?