What surprises me about the Saarloos trade is not that Kirk was traded, as he was one of several "back-end-starter types" on the current roster and likely already had his "career year". The A's probably felt they couldn't afford enough mirrors to squeeze another solid year out of Saarloos.
What I would not have anticipated was that the A's would acquire another reliever. If you think Oakland has too many "back-end-starter types" in the current mix, look at the cast of characters vying for middle relief attention. When you make your list and actually forget about Witasick (which, by the way, is a nice feeling), you know you're knee deep in repetitive parts.
The A's farm system is not in good shape. Saarloos was not going to net the kinds of prospects that could single-handedly change this fact. But while rolling the dice with some lower-level prospect who could turn out to be a hidden gem, looking at a farm system and 40-man roster that is rich in relievers but not much else, why pick up yet another middle relief guy? That's the part that has me puzzled.