Midfield
Assuming Emery fields a 4-4-2, the midfield will be anchored around two deep midfielders - probably Granit Xhaka, and new signing Lucas Torreira, who has been pegged to be one to look out for. This is assuming Aaron Ramsey who is injury-stricken, and only returned to training this week will not be fit enough to play.
The other two midfield choices seem easier to make, with Mesut Ozil (the more obvious choice) and Mkhitaryan to act as the ideal pairing to start out wide, the former on the right and the latter on the left.
The question of deep midfield starters entirely depends on fitness levels. Torreira and Xhaka returned late from the World Cup, while Ramsey has only just returned to the training ground after a calf injury.