Arsene Wenger has revealed that Laurent Koscielny is struggling with injury ahead of Arsenal's Champions League qualifier with Besiktas on Tuesday.

Koscielny played 90 minutes in the Gunners' 2-1 win over Crystal Palace on Saturday, but Wenger claims that the victory came at a cost.

The French coach revealed that he will now accelerate Per Mertesacker's return to first-team duties following an extended holiday after winning the World Cup.

"We will assess Koscielny on Monday; if he's fit and capable to play, we play him," he told the club's official website.

"It was our plan to bring the Germans back in contention for Everton. But in case of emergency I will take Mertesacker.

"But we have Bellerin, who was 19 today, who can come in. we are a bit short. I hope Koscielny responds well."

Tomorrow's clash is scheduled to kick off at 7.45pm.