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However Arsenal already has Trossard and Martinelli. Nico Williams should definitely be used on the left to get more efficiency. I wonder what kind of changes Arteta will make in case of signing him. Maybe he might try Nico on the right anyway to compare and then decide.
My prediction is that this transfer will not happen.
Let's pay attention slowly, if this transfer really happens, it will not be possible for Nico Williams to replace Saka position and on the one hand, as you said, if Arteta forces Nico Williams to be in the LW position, that will also not be possible because of Martinelli and Trossard much better and more experienced to compete in the EPL.
Arteta cannot possibly make a decision too quickly because since Arsenal have been getting closer to the EPL title for 2 seasons, Arteta will choose new players carefully and see what experience and skills the new players he will recruit later have.
Or maybe there is another option of making Nico Williams a second tier player and that would make more sense because Arteta really needs reliable players to be able to win the EPL title and I don't doubt Nico Williams even though he doesn't have experience in the EPL but I know how skilled he is in dribbling the ball and very agile.
Arsenal deserves to be associated with this player because Arsenal characteristic is always to choose young players to recruit as new players, but for me that won't happen.
And what I'm saying right now is just speculation because this season's break is still very long and a lot can still change.