The German is set to miss five months of the season after picking up an injury.
The defender picked up an injury in the recent friendly with Lens and is now set to miss the first five months of the season.
It has left a major hole the heart of the Gunners defence, which is also set to be without Laurent Koscielny for the start of the campaign after his exertions with France at Euro 2016.
Arsenal's Theo Walcott, Mathieu Debuchy, Kieran Gibbs and manager Arsene Wenger
Arsene Wenger has admitted they will enter the market for a defender to try and fix the issue, but Gibbs says the German’s absence is actually a chance for the youngsters to impress instead.
“Per is a big loss on and off the pitch as he is one of our biggest characters and a leader,” he told the Mirror.
“We are a young squad in general and with Per out for a few months it is a good opportunity for the young players and for those looking to become more senior and fill his role off the pitch.”
Arsenal's Calum Chambers in action with Hull's David Meyler
One man who should be looking to stake a claim is defender Calum Chambers given the lack of opportunities he had last season.
He has fallen down the pecking order after a strong start to life at the Emirates, but this injury to Mertesacker presents him with a chance to get his foot in the door once again.
It remains to be seen if he can take the opportunity or if Wenger makes a move to sign a replacement before the end of the window.
Arsenal manager Arsene Wenger