Unai Emery was left frustrated after he was pressed over Mesut Ozil's future at Arsenal following his decision to leave the playmaker out against Vitoria SC.
Ozil has featured just twice for the Gunners this term, starting against Watford and Nottingham Forest in the Premier League and EFL Cup respectively.
However, the 31-year-old is yet to be named in a Europa League match squad as Emery continues to omit him from the first-team picture.