Kieran Tierney could be out for up to three months with a thigh injury.
The defender picked up the knock during Real Sociedad’s clash with Athletic Bilbao on Saturday.
The Arsenal man went off prematurely after just 20 minutes in a match that Sociedad won comfortably 3-0.
Tierney has made five appearances for the Spanish side, including in the Champions League.
This new injury will be a further blow to his hopes of impressing suitors who want to see him in action.
This is obviously another blow to Arsenal, not allowing them to watch their on-loan player progress.