Laurent Koscielny has been sent back to Arsenal by France to undergo tests on an Achilles injury.
Koscielny has struggled with pain in the tendons on both of his feet, with reports in France saying that he has acute tendinitis.
Arsenal is very thin at center-back after selling Thomas Vermaelen to Barcelona in the summer. Arsene Wenger said that he would sign a specialist replacement. But he aborted the plan after Calum Chambers, who is nominally a right-back, impressed in central defense in the early matches of the season.