I think what makes an atg valuable is his age. Potential, if not maximized, we are talking minimum 125-130 TSP here dont hold much value in the transfer list. So i do think his value is greater now than when he reaches 20 and he doesn't look the part. You can reach 130 TSP with an advanced level though it would be easier and faster to hire a better trainer. I have seen 150+ hof players and you have an ATG. Try to reach out to your Senior coach. I personally would keep him because it is very rare to draft one. You cant train potential. Lower potential you can find that every week in the transfer list. If you decide to cash in make sure your nt coaches know they may be able to find someone to take it off your hands.