Although flying high at the top of the league, Arsene Wenger's men have kept just one clean sheet all season, and the center back insists they must concentrate more at the back
The Gunners have scored 18 goals in their opening eight league fixtures but nine conceded is joint-worst defensive record in the top six, and the German defender insists they need to tighten up at the back.
"We know we are on a good run, but we know it needs more than just playing with full freedom and vision - we need to defend first and then we can switch the rest on," he told the Evening Standard.
"You have seen what can happen after that.”
Last weekend’s win over Norwich saw Jack Wilshere score one of the best goals of the season following some intricate interplay on the edge of the box, and Mertesacker admits he is excited by the attacking options at Arsene Wenger’s disposal.
"We have players who can play so quickly together," he explained. "Tomas Rosicky came in and fitted into everything as well as Mesut [Ozil] or Jack [Wilshere].
"When those three combined together, you could feel some magic in the air, a real chemistry.
"Mesut does not need to adapt to our style because he is a natural talent. You could see that against Norwich, when we played such good football."