I did a search for threads on this year's outfield and came up with nothing after April of 2012, so if I missed a thread, my apologies. That said, with the Carp deal being reported, it seems the Sox have pieces of the outfield they'll start 2013 with and there is some discussion on how that's going to break down going on in the Carp thread that I thought I'd nudge this way before it gets too derailed.
At present the team has Ellsbury in CF and Victorino in RF. Left field will be played by a combination of Gomes, Carp, Nava and Sweeney with one of those three not making the major league club. Only Nava has options left. Down the pipeline, they have Jackie Bradley hoping to see a promotion later in the year and still have one and a half legs of Bryce Brentz in Pawtucket along with Hazelbaker, Linares and Hassan as depth.
The discussion started here, and this is the last post in that thread about outfield composition.
Carp has no options left, so he can't be stashed. Sweeney is on a minor league deal that he can opt out of if he doesn't break camp with the big club. Nava is the only one that has options and can be sent down. So I think, barring injuries, the most likely scenario might be Sweeney and Carp on the 25-man and Nava at Pawtucket.