Mertesacker inked new terms with the Gunners this week.
"For Per I'm happy," Koscielny told Arsenal Player. "It's his third season here and he signed a new contract. I think he gives everything for the Club, it's a man who is respected by all of his team-mates.
"He's a German so he's professional and it's very important to have a partner like him in the squad. He tried to give himself for the team and when the other players see that, they want to do the same."
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