Centeno is a really, really bad hitter - his performance at the plate this year has actually been incredibly good, by his standards. But there is no reason to think he can sustain it. Garver is already a better hitter than Centeno, I have little doubt about that. So if his defense is acceptable, I don't see why he should be kept in the minors. It's not as if he's a 21-year old, high-upside prospect that you don't want to mess with. If Suzuki is dealt, it could be Garver's best and even only opportunity, if the Twins gave it to him. I guarantee he would be thrilled.