Post us his profile pages, contract,personal,history and your tactic, and how you play him. it can help us evaluate the problem better, but i highly suspect that the answer NiallZemin gave would be the correct one.
He's only 19 and played 15 times for us, we finished 6th in the Championship, playoff final runners-up.
I assume his main reason being his average rating just 6.60?
Also he's on loan at Yeovil for my new season