His strength/speed endurance at high speed is his real strength, he's a bit like Rooney in that he's got a man's body at 17, but he needs to do a lot of work of the technical/mental side of his game in my opinion, I think a year with the U21's will do good for him, hopefully followed by a Championship loan.
A lot of potential with those natural physical attributes, I don't think he'll be ready to be a PL starter for a few years yet