Why couldn't he play Shooting Guard? Although he appears to be a poor defender, maybe the size would help against "corner 3" type guards. Guarding LeBron is a lot harder than guarding Monte Ellis, or Ben McLemore.
I mean, all of these college guys are going to be absolute dreck on defense unless they commit to it, so there could be hope. While I am interested in others' thoughts as to why he couldn't play SG, I can say that I am much, much lower on him as a small forward... ...SF is the dominant position in the NBA right now, as the top three highest scoring players are SFs, and 5/10 of the top scorers are SFs.
This kid has a nice shot, and can play the pick and roll - but he just won't get into that class, IMHO.