The defender has joined from Lille for a fee of around £27m and will strengthen the Gunners defence.
The Brazilian was a priority for Arteta but while this deal took a while to get over the line, the next should be much quicker.
That is because Arsenal technical director is moving forward with plans to bring in more players.
One should be fairly recognisable at the Emirates with Dani Ceballos primed for another loan from Real Madrid.
A deal has already been agreed and it just a matter of time before the Spaniard rejoins the Gunners for another season.
The transfer will please Arteta, who outlined his plans for the midfielder last week.
"Well, we have some talks and Dani knows really well what I think about him," he said.
"He was pretty clear with me as well that his intention was to remain with us but obviously Real Madrid is involved and I don’t know yet what they want to do with the player.
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"But he’s a player that we are interested in because we really saw, in the last few months of the season, what he is capable of bringing to us."
The next player in Arsenal's sights is Lyon hotshot Houssem Aouar, who has drawn many plaudits.
The Frenchman wants a move to the Premier League and the Gunners are keen on becoming his destination.
However, Lyon would not let the midfielder go cheap and Arteta may have to sell players in order to make a transfer.
Another midfielder Arsenal are looking to sign is Thomas Partey, who has been at the centre of a transfer plot all summer.
The north London outfit have not given up on the Ghana international but Atletico Madrid have demanded that his full release clause be paid.
That stands at £45m, meaning Arsenal will have to sell players - much like the case with Aouar.