You can see it in his fade throws on film. Watching him in the games I've been really impressed with how calm he has stayed under pressure. You see it on a couple of the highlights - with a rush in his face he still steps into the throw and delivers it exactly where it's needed.
I think with how his body has matured this past year he can explore a lot more of what his athleticism can do for him, but he's got a solid arm. He's always been tall for his age, but a bit on the thin side. Now he has filled out and tha can be a huge asset - in the meantime I think his frame really helped him focus on his passing game and not rely on athleticism, which shows.