Mesut Ozil was a notable absentee as Arsenal headed to Greece on Wednesday ahead of their Europa League clash with Olympiacos.
The German playmaker stayed at home “due to personal reasons”, Arsenal said.
Arsenal did not provide further information, but reports said Ozil’s wife, Amine Gulse, was close to giving birth.
Head coach Mikel Arteta will have limited options in the centre of the park for the first leg of the last-16 tie.
For Arteta, the fixture is his first European game in charge of the team since succeeding previous first-team boss Unai Emery.
Ozil’s fellow midfielder Lucas Torreira also did not travel, with the Uruguayan unwell but being assessed with a view to him taking a later flight to Athens should his health show a “significant improvement”.
The unavailability of Ozil means the World Cup winner has missed all four of Arsenal’s Europa League away games this season.