In T.R. Sullivan's notes today, he seems to indicate that Adrian Gonzalez and Phil Nevin will be platooning in the DH role. Showalter indicates that he wants Gonzalez starting against righthanders, so unless Buck is willing to playing Nevin in the outfield -- something that, given Mark DeRosa's constant presence out there, seems unlikely -- a Gonzalez/Nevin platoon at DH appears to be the most likely scenario.
Sullivan also says that the Rangers are going to look at dealing Nevin before August 31. While I don't know if Nevin has already been sent through waivers, my guess is he probably has been, and he's a lock to clear because no one is going to want to put in a claim and be stuck with his contract.
If the Rangers could flip him, eat most of his contract, and pick up a halfway decent prospect, it would be a success.