Looking at the numbers, it seems like if the Wizards lose Ariza in free agency, that they would be willing to take Green in a salary dump to squeeze out a bit more cap space for the Celtics to sign a free agent such as Carmelo Anthony. I don't think Washington would have the cap space to completely absorb Green's salary, but something like Green for Miller and a second might be doable to clear almost $5m from payroll.
One thing to watch for is Ainge finding a way to get involved as a third team in a deal that sends Gortat or Ariza to another team in a sign-and-trade. Does anyone like Gortat or Ariza enough that they would send Green plus another asset to Washington to faciliate a sign-and-trade acquisition of either player?