Before we talk about Kyle Schwarber (and a little Bryce Harper), let's point out that in the old days, a defender built a reputation and kept it more or less forever.
Bernie Williams was a good example of that. For the first few years of his career, Williams was a good outfielder. He had above-average range. Williams was as solid as they come. He was legitimately good, maybe even Gold Glove Award good. Then in 1997, with the Yankees right in the middle of their dominance, people began noticing. Williams began getting acclaim for his defense.