He's an excellent fielder, but I don't think he had a great year defensively. Although his struggles around the wall have been exaggerated here at times (but there is some truth there), he's surprisingly shaky when charging ground balls. He has bobbled a few and often slows down more than he should to make sure he fields them cleanly. These are areas he can clean up with more reps and experience (and practice, although that seems like a forgotten concept at the major league level). Still, I'm pretty confident he'll be a top-10 center field defender for several years.
Solid analysis. In a sense, his defensive game is similar to his offensive game. He's got some nice tools, but there remains a fair amount of untapped potential. I hope he's able to grow into his defensive game the way he appears to be developing on the offensive side. He's got to get a little more aggressive out there so he can make some tougher plays -- right now, he's just a bit tentative. The play at the wall on the night they clinched may boost his confidence some -- I hope so.