Captured South African journalist Shiraaz Mohamed is alive in Syria and could be home within a month.
Mertesacker and his Germany teammates Mesut Ozil and Lukas Podolski were given the extended break by Wenger after the World Cup triumph in Brazil last month with the trio scheduled to miss the first few weeks of the campaign.
However, defenders Laurent Koscielny and Kieran Gibbs suffered knocks in Saturday's last-gasp 2-1 win over Crystal Palace in their English Premier League opener meaning Mertesacker, who announced his international retirement last week, could be drafted in to play in Turkey.
"We will assess Koscielny," Wenger was quoted as saying by British media yesterday.
"If he's fit and capable to play, we play him. It was our plan to bring the Germans back in contention for Everton [on Saturday]. But in case of emergency I will take Mertesacker.
"Ideally he would need one more week preparation, but he's willing to play, no problem. We are a bit short."
Frenchman Koscielny drew the Gunners level on the stroke of half time on Saturday after Brede Hangeland's glancing header gave Palace the lead at the Emirates Stadium. The centre-back played the full 90 minutes but suffered from pain in his foot, while Gibbs lasted little over an hour before succumbing to a hamstring injury.