If a midseason AGon trade happens, i'd think the M's are the most logical choice. They could be in a playoff chase (unlike the O's), they have an average 1B (unlike Red Sox) and they have better trade pieces than us.
If it gets to next offseason, then the Sox (both colors) have a better shot, since the Padres won't be able to demand high end MLB guys like Ellsbury or Beckham anymore.
Also maybe we get some breakout guys in our system this year that give us better pieces than we have now.