I dont think there is much of an argument as he is not ready by a long way. I do however think that CH is not 100% convinced by DS hence wanting competition for him.
He is not ready for a season as No 1 in the chanpionship yet, odd games but not 46 if DS was injured or played worse than last season so a loan will give him valuable experience, which will benefit both him and us.
I would sooner we sent him out for a season loan to play and brought in somebody...