Mertesacker this week penned new terms.
He told arsenal.com: "When I think something goes wrong, or that we need to be aware of a situation that my experience has shown over my 10 years in professional football, I have to go and tell. That is what I am doing at the moment.
"It took me a while to realise I can be a main part of this squad. Now I want to show that. We need to get everyone ready at this club and get the best out of everyone. There is the right balance in this squad and everyone takes their place."
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