That doesn't make much sense. Training his secondaries first will give you a great advantage in the long run. His primaries will still train quick enough due to his size. You don't have to rush. Take your time to take advantage of such a potential.
If you really can't afford him any longer, sell him. If you see that coming, get yourself another trainee now with less potential for little money who you can keep. Otherwise you'll wast a lot of potential, i.e. money.