Given that Dan Johnson and Esteban Loaiza will join Mark Kotsay on the DL to start the year, there are basically two roster decisions remaining: Lenny DiNardo vs. Brad Halsey as the long man in the pen, and Todd Walker vs. Travis Buck to replace Dan Johnson.
Even though Buck is probably a better player right now, I expect the A's to let Buck simmer some more in AAA, and give Walker a shot. Walker's slugging percentage slipped under .400 last year, but he still put up a typical-for-him .356 OBP, which ain't bad. Most of that drop came from a collapse against LHP (.204/.320/.315), which is actually fine, since Bobby Kielty has the same issues from the opposite side of the plate. This makes for a nice platoon, with Swisher covering the position for the sitting half of the platoon. How's this for some platoon numbers:
2006 vs LHP (Kielty): .325/.358/.607
2006 vs RHP (Walker): .302/.368/.425
Walker's slugging still isn't great, but the total numbers will do fine. Only problem is, this requires Shannon Stewart and Milton Bradley to stay healthy, so the A's can avoid playing Kielty against RHP and Walker against LHP. I suppose if that situation does come up, that's where you try Antonio Perez in the outfield and see what he can do.