Arsene Wenger believed his Arsenal side showed a lack of focus and complacency in the first half against Östersunds FK on Thursday night, as they progressed to the last 16 of the Europa League on aggregate.
The Swedish side fell to a 3-0 defeat in the first leg last week, but managed to pull off a shock win at the Emirates - scoring twice in the space of 69 seconds to cause an early stir in the last 32 tie.
Hosam Aiesh’s shot was deflected into his own net by Arsenal defender Calum Chambers after 22 minutes, and it was quickly followed by winger Ken Sema slotting home a second for the visitors after some excellent footwork.
Just minutes after the second half begun, defender Sead Kolasinac eased the nerves of the Arsenal faithful with a right-footed firing finish to help his side progress into the round of 16.
Wenger, however, was not happy with what he saw, saying - via Sky Sports: "We were not at the races in the first half. We were in trouble because we were complacent and not focused. We were open every time we lost the ball and had no ideas with the ball. That's why we were in trouble.
"In the second half, it was much better. Our energy was high and our domination as consistent. Overall we responded very well. We did the job to qualify. That's what you have to keep from the night and that's it."
Arsenal now face Manchester City in the Carabao Cup final at Wembley on Sunday, and await their fate in the Europa League last 16 draw - which takes place on Friday at noon.
He added: "We prepared properly, in a serious way, but you have external circumstances. The fact that we won the first leg 3-0, the fact that we have another big game on Sunday, the fact that people subconsciously think they just have to turn up to win the game.
"Football doesn't work like that. We played against a good side and it's what you see in the FA Cup. You can be in trouble every time you're not 100 per cent focused. I felt in the first half the whole team was not at the level you expect. It was not easy for the defenders because we lost the ball too early and we didn't screen well when we lost the ball."
Wenger also addressed injury concerns to Jack Wilshere and Alex Iwobi, who left the pitch despite still searching for the equalising goal.
He added: “Iwobi had a cramp. Wilshere is not injured, he is OK.