Arteta admits the fullback is on the outer due to better performing teammates ahead of him.
He said, "Sometimes (it's the) performances of other players as well. You can be at a really good level but somebody can be at a different level, or it’s just that I have the perception at the moment that it's better to play or start somebody else in the team.
"It doesn’t mean Myles has done something wrong at all, completely the opposite. So when he has the chance, he has to try to show the level that he's at, elevate it, and make the decision even harder."
On Lewis-Skelly playing in midfield, Arteta added: "Yes, fluid. Especially because if you look at the amount of time that Myles defends and attacks in certain spaces, he's much more a midfielder than a full-back.
"But there are moments that he needs to be in that position. He can absolutely do it. He's shown it. He's done it at the highest level in the Champions League so there's no question about that."