I wouldn't train him as his age will slow training down. He can be your franchise player, but I wouldn't make him my trainee. If you want someone to train, look on the transfer list. At the beginning of the season, there is always a lot of buying and selling going on. Look for 18 year olds with at least star potential. Try to buy someone with good skills, but for a low price. There are plenty of players like this that can be molded into players that your team can use, if you are patient.