To be honest, I would train his guard skills first. Trust me, from personal experience and experiences of other managers, it is better to train secondaries if you are planning to train them anyway. His OD is the only thing you need to worry about for now. I know a user who has a 6'8" and 6'10" big who he started training OD from when they were first drafted. As of right now, their OD is at proficient or prominent. If he were to sell them, he would make a lot more profit than if he had left them with their bad skills. But it is your decision.