They should trade him. They don't have space for him and he's been good -- great if you go by traditional stats (ERA). He's a good depth piece, but you're wasting his value in the minors.
Or they could keep Milone and sell very high on Chavez, but I wouldn't make that move unless it was a no-doubter. Literally all five guys in the Athletics rotation right now (Shark, Gray, Hammel, Kazmir, Chavez) are having career years.
Which, btw, is f***ing stupid. The A's of the past few years have to be one of the luckiest teams ever in terms of guys panning out or having the best years of their career, whether it's the pitching, or whether it's Reddick, or Lowrie, or Cespedes, or Donaldson, or Moss, or Norris, Crisp, Jaso, or just about any f***ing player on their roster. Even their relief in Doolittle, Gregerson and Otero is ridiculous.