Yeah he is Arteta's perfect inverted full back. There is no way Arteta is moving him from that position. He really does have it all mental, technical and physical.
Read an article the other day about how he has freed up Martinelli a bit through passing out to him a lot quicker but also with his runs occupying the space inside to prevent double teams on Marti.
And if he is left open on the inside he is a threat (goal v Man C + assist v Real) so it's a risk to leave him free.
He is basically the key to unlocking our left side.