Gael Clichy could be unavailable for up to a month after Arsenal confirmed that the France left back has a suspected stress fracture in his back.

The North London club face AZ Alkmaar in group H of the Champions League tomorrow night and Arsene Wenger, the Arsenal manager, is expected to select Kieran Gibbs to replace Clichy.

"We have lost Gael Clichy with a back injury which was not expected,” Wenger said. "It looks like he could be out for a while. We fear a stress facture of the back. We will know more about that tonight, but if that is the case he will be out for a few weeks."

Nicklas Bendtner picked up a groin injury in the victory over Tottenham Hotspur on Saturday and Wenger is unsure of how long the Denmark forward will be out. “Nicklas we still don’t know yet, but it will be at least four weeks," he said.

Wenger is not worried about the inexperience of Gibbs, 20, despite the England Under-21 international having a poor performance against Manchester United in the semi-final of last season's Champions League. “I have every confidence about Gibbs. I have said that many times."