Theo Walcott was forced to sit out of this morning's training session, just one day before Arsenal take on Olympiakos in the Champions League at the Emirates Stadium.
The England international injured his knee during the Gunners' weekend victory over Bolton Wanderers.
At the time manager Arsene Wenger confessed that he was unsure as to how serious the problem was, although the club have since confirmed that it is only a "minor" injury.
Arsenal drew their first group fixture 1-1 with Borussia Dortmund.
