If Kobbie Mainoo lost his place in the team, I won't blame Carrick, I will blame him for his negligence.
Truly, you went to the World Cup, but you didn't get any minutes there. Any serious player should have rested for just a week and returned to the club immediately to start fighting for his place.
But he looks so relaxed at home as if he's position is already secured while Andrey Santos and Mason Mount are doing the same thing he does and even better.
If he loses his place in the team, that will be on him.
And whatever decision Michael Carrick makes on him, I support it wholeheartedly.