Jack Wilshere felt Arsenal were guilty of underestimating Ostersunds after the Premier League club flirted with an embarrassing exit from the Europa League on Thursday.
Arsene Wenger's side appeared to be in complete control of the last-32 tie after cruising to a 3-0 win in the first leg on Swedish soil, giving them a comfortable cushion ahead of the return fixture in north London.
However, Ostersunds scored twice in the space of 70 seconds in the first half at the Emirates Stadium to suddenly put the tie back in the balance.
While Sead Kolasinac's goal shortly after the break ended the visitors' hopes of completing an improbable comeback, Wilshere knows the home side had turned in a below-par performance ahead of Sunday's Carabao Cup final with Manchester City.
"We were nowhere near it, especially in the first half," the England international told BT Sport.
"We weren't good enough. To be honest, we did improve in the second half but it still wasn't good enough.
"We're through and that's all that counts, so we will see who we get in the draw. We have a big game to come on Sunday too, so we can focus on that.
"But when you're 3-0 up in a two-legged tie you still have to go again — it was only half-time. Maybe we underestimated them a little bit, but the main thing is we're through."
Despite suffering a 2-1 defeat at home, Arsenal triumphed 4-2 on aggregate to secure a place in the last-16 of the tournament, with the draw for the next round taking place on Friday.