The German international defender pleased with the start the Gunners have made and he believes that newly tightened back-line has been a major factor in their opening few games
The German international has made six appearances this season for the Gunners, who have conceded only five goals, the second fewest in the league, Mertesacker believes the defence has been the key.
"It can be the difference, it is crucial for us that the defence is winning more than just games," Mertesacker told Sky Sports. "We must try to keep that in our mind the whole year.
"We have not conceded a lot of goals during games this year; most have been from set pieces. We just need to keep concentrating on our defensive level."
Arsenal’s defence has been much maligned since the 'Invincibles' era of 2004, and under the watchful eye of new assistant manager Steve Bould, the back four are blossoming.
Mertesacker, however, believes that the club's strength in depth in defence has helped and that they can go from strength to strength.
"The manager told us before the start of the season that we have a lot of good centre-backs and is convinced we can make the team stronger and stronger because we have a lot of those good players in every position," he added.
"The manager said he would change sometimes and I think that's great for our development."