2. Sami Khedira
While Arsenal do have defensive problems, they still need a central midfielder who can control the game. They have Coquelin doing a pretty good job but that is in a more defensive role, Arsenal need someone like a Kroos or a Carrick and Khedira could just be that player. Khedira will be out of contract next season and that should be good enough for most clubs to chase after the World Cup winner.
Khedira might have had an injury plagued season and has been out of favour at Real Madrid but he still is one of the best players in his role if he gets going and with him being available on a free, Arsenal should snap him up before some other club comes calling.