Arsenal manager Arsene Wenger has confirmed that midfielder Francis Coquelin is expected to be out for three weeks with a knee injury.
The defensive midfielder suffered the problem during last Saturday's 3-0 victory over Chelsea at the Emirates.
After the match, Wenger, who was celebrating 20 years in charge of the Gunners, admitted that he was "worried" about the damage, particularly as Coquelin missed two months of action last season with ligament damage.
Ahead of tomorrow's Champions League meeting with Basel, Wenger told reporters that he will be without the midfielder for around three weeks after receiving "positive" scan results.
Coquelin's absence could give Granit Xhaka a chance to earn regular first-team minutes following his £30m move from Borussia Monchengladbach in the summer transfer window.
