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You would have to pay all of his salary to get anything in return, and even then it wouldn't be much. It would be far better to keep him because he is the perfect mentor for Montero. He's Latino, seems to have a good attitude, has tons of experience yet isn't a Jorge Posada-type former star whose past glory makes him feel entitled. Olivo is both nearing the end of his a career and Montero is truly special so it shouldn't be a problem for Miguel to adjust to being a bench player.
Not to mention that it's always good to have depth, which the M's don't have at catcher.