Agreed with the above poster. He's short of time to make the U21 as a trainee, but I have two guys that are 23 that I train and regularly receive pops.
That said, you're asking for advice on how to train him. At this point you should definitely look at his offense- his FG% and 3pt% are terrible. Personally I like training/acquiring players that fit into my system; if you run a perimeter offense you should definitely look at JS/JR. If you run an interior offense, maybe push his DR and IS upwards more. Either way, he seems to be very strong besides his shooting, so you've a good player on your hands.