The 6ft 6in German centre-back produced a composed display alongside captain Thomas Vermaelen as the Gunners battled to a 3-1 win at West Ham.
"It can be the difference, it is crucial for us that the defence is winning more than just games. We just try to keep that in our mind the whole year," he said.
"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."