#4 Santi Cazorla
Santi Cazorla is one of the most underrated players in the world. His presence on the pitch for Arsenal was so important to the team that no one has managed to replicate that for the Gunners.
The Spaniard was good creatively and defensively but his injuries have kept him out for long periods of time. It's been so long that one actually needs to google to find out when he last played a game.
Some fans and almost all of the rival fans would have all but forgotten that the little Spaniard is still at the club. Thus, signing his replacement is a must for Arsenal. Granit Xhaka, Jack Wilshere and Mohamed Elneny together have not managed to fill his boots, and that makes you wonder who in the world can do that right now.