His trickery on the ball and eye for a pass has left some supporters already calling for a permanent deal to be lined up for the next summer transfer window, but it could be a difficult one for the club to get over the line.
The 23-year-old has already made it clear that he wants to prove himself at Real Madrid, after previously falling out of favour in Spain.
He arrived in Madrid with a lot of promise but is yet to showcase his true talent under Zinedine Zidane.
This means that Arsenal may have to go searching for an alternative next summer. We’ve taken a look around Europe at some of the midfielders that they could target instead.