Castro has all the physical tools to stay at SS. His problems are mostly from footwork and decision making... two issues which I do not see as getting better as a result of moving to 3B. The extra time at 2B might be of some use if he doesn't figure it out in a few years though. But I really do mean a few years... unless he gets significantly worse in a hurry, I don't want to see Castro moving off SS before he's 24-25.