The Gunners travel to Istanbul on Monday ahead of the first leg of their double header with the Turkish side, but injuries suffered during their opening day win over Crystal Palace have forced Wenger to change his plans.
Laurent Koscielny and Kieran Gibbs both picked up knocks, and now Wenger has brought Mertesacker back early as he had planned to give him and his other German World Cup winners extra time off.
But Mertesacker will now be on the plane to Istanbul and could feature for Arsenal.
"I planned to bring the Germans back in contention for Everton but, in case of emergency, I will take Mertesacker to Turkey," Wenger said.
"It's a bit early for him - ideally he would need one more week preparation but he's willing to play, no problem. We are a bit short."