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Players like Ackley also come with contractual concerns and the desire to max their service time. Testing them and having them bat .200/.250/300 isn't good baseball. That's setting them up to fail and there's a bigger possibility that you'll retard their development, rather than helping it. All while getting closer to the Boras Line.
With regard to Wilson, it's Z's job to pick what players go where. Obviously, he doesn't see Wilson as a good player. That's his call to make.