Defender Per Mertesacker admits the 2-0 defeat at Southampton on January 1 was a wake-up call for Arsenal.
Questions were raised over Arsenal's defensive department at the end of a game in which goalkeeper Wojciech Szczesny made two terrible mistakes.
But the Gunners bounced back in style to register back-to-back victories including an impressive away victory at Manchester City.
"Southampton was a major setback - it was a bad start to the year," the German told the club's official website.
"After that, we promised ourselves to come out of that comfort zone and be a bit more focused, especially [to know] that what comes first is defensive work and not just for the back four.
"That was maybe the main thing for us to focus on, and afterwards we played more convincingly, especially defensively.
"You can see the benefit when everyone realises that, and I thought everyone realised it very quickly after we lost at Southampton.
"Maybe sometimes you need a wake-up call to realise what is really important. We worked a lot on our defensive shape, not just the back four, to avoid those dangerous free balls against us.
"We look much better and the best game defensively was against Man City - that was a bit of a change.
"In the last few years, we went there and wanted to convince everybody that we could play our own way, so it was a bit of a change [this time]. Sometimes we have to do something unexpected, and that was maybe the winning moment."
