Arsenal survived a major scare to secure their spot in the last 16 of the Europa League despite suffering an embarrassing 2-1 home defeat to Ostersunds, who could be backed at 11/1 with Sky Bet for the win before kick-off.
After building a commanding 3-0 lead in last week's first leg in Sweden, Arsene Wenger's Gunners appeared to be coasting into the next round, only for two goals in 70 first-half seconds to send a half-empty Emirates Stadium into panic.
A Calum Chambers own goal and a neat finish from Ken Sema had Graham Potter's side two goals up at half-time - and the hosts were jeered off by a restless, if reduced, crowd.
Sead Kolasinac thumped home a response early in the second half to mark his first start since New Year's Eve with a vital goal.
That was as good as it got for a disjointed Arsenal outfit, who now face an altogether different test when they face Manchester City in the Carabao Cup final on Sunday.
Atletico Madrid head the betting at 11/4.
Gunners midfielder Jack Wilshere told BT Sport: "We weren't good enough. We improved a little bit in the second half but we still weren't good enough.
"When you're 3-0 up you still have to go again. Maybe we underestimated them a little bit, but the main thing is we're through.
"We're through, that's probably the only positive. We can't start a game like that and expect to compete at this level."
Ostersunds boss Graham Potter told BT Sport: "I'm very, very proud of the players and the supporters.
"To play in the manner we did we showed real courage, real bravery and played some good football against a top team.
"The objective is to go through. At 2-0 we felt we had a chance, we did what we wanted to do in terms of we played well and won the game, but we were short of the miracle."