I took a look at your roster and to be honest there isn't that "stand out" guy who is just begging to be trained. Your younger guys don't have a great deal of potential so they'll probably cap earlier then what would be ideal...
Darrell Ennis is probably your best trainable player for this year. However I'd look to the draft for some fresh talent to train after this season. Darrell has good potential, but based on his age he's not the best option for your squad if you've got a younger guy with equal, or maybe even slightly less potential.
If you haven't it would be prudent to do some draft scouting to help you find that piece to really start to work around.