Saliba, who has expressed his wish to go back to Marseille next year and play in the Champions League, signed for Arsenal in 2019 for £27m from St Etienne but has yet to play a competitive game for the club.
Arteta said: "He has to come back. He has the experience and environment to be competitive with us. We made the right decision [to loan him out].
"If he had stayed with us this year with Ben White and Gabriel, he would not have had half the playing time he had with Marseille.
"For his growth and what he can do next season it would not have been good.
"William was not with us because he would not have had the playing time to gain experience. That's all, there's nothing else."
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