Aberdeen battled back to secure an excellent draw in Gothenburg thanks to two second half goals in four minutes.
The Dons are aiming to progress to the group stages of the Europa League for the first time in 15 years, but looked down and out after going two goals down with the second a penalty after a VAR check against Jack MacKenzie for handball.
But Bojan Miovski fired Aberdeen back into it before unlikely hero Nicky Devlin scored his first goal for the club with an excellent clipped finish.
And they could even have won it in injury time after a Jamie McGrath goal was ruled out for offside.
FAMILIAR FACES
This was Aberdeen's fourth game of the season and the third time in a row that manager Barry Robson picked the same team.
Despite new faces brought in this week, Robson resisted the temptation of bringing in international players Richard Jensen and Jamie McGrath straight into the line-up, along with New Zealand international James McGarry.
All three were on the bench with McGrath and McGarry impressing when they came on. He opted for his tried and trusted 3-5-2 which was in reality a 5-3-2.
That meant the central defence featured Nicky Devlin - predominantly a right back - with young Jack MacKenzie alongside giant Serbian stopper Slobodan Rubezic.
It also saw Ryan Duncan again asked to fulfil an unfamiliar left wing back role again.
Angus MacDonald - who was such a success last season - was only deemed fit enough for a place on the bench despite getting some minutes under his belt in last week's Viaplay Cup win at Stirling Albion.
Jonny Hayes was the only starter from that 2-0 defeat in Gothenburg two years ago and he was on the bench too.
HACKEN'S HOME COMFORTS
Aberdeen had already suffered defeat at Hacken's modest Bravida Arena and they were going into the ground labelled as 'Fort Knox' by the Swedish media on account of their outstanding home record.
The Dons had lost here two years ago but had the considerable insurance policy of a 5-1 first leg win as a cushion.
They boasted an unbeaten record there since April and had rattled in 50 goals in just 20 league games as they attempted to retain their Swedish title.
However, there were flaws in their make-up and Aberdeen certainly exposed them. They were eliminated from the Champions League by Faroes minnows Ki Klaksvik after a penalty shootout following a 3-3 draw.
And Welsh side The New Saints had managed to score here too in an earlier round.
Managed by former Norway boss Per-Mathias Hogmo, they were always going to have a go here and showed their attacking intentions immediately by winning two corners in the first two minutes.
Aberdeen were backed by 500 travelling fans - most of whom had made the pilgrimage to the Ullevi Stadium in the city where their team of course triumphed in the European Cup-Winners Cup Final against Real Madrid in 1983
DONS SLICED APART
Hacken's opening goal was a well-worked effort and showed their quality up front.
Captain Samuel Gustafson - who was excellent throughout - dissected the Aberdeen defence with a pass to Ibrahim Sadiq and too many visiting players were too far up the park to react. It was teed up to Amor Layouni and the Tunisian striker easily converted.
In fairness, the hosts could easily have scored a couple of more times in the first half. Sadiq flashed a header just wide from point blank range and he gave Jack MacKenzie and Ryan Duncan a torrid time with his flicks and tricks.
The Swedish champions have an abundance of talent up front. As well as Sadiq, they have Layouni and Romeo Amane in a front three that caused Aberdeen no end of problems.
Aberdeen may well line up differently at Pittodrie with new personnel, but they will still have to find a way of dealing with that front trio of attackers.
HACKEN VULNERABLE
We'd heard a lot about the threat posed by Hacken up front, but let's not kid ourselves here - their defence can certainly be got at as Aberdeen proved.
They looked sluggish in defence and uncomfortable on the ball. Aberdeen boss Barry Robson said after the game his side could easily have scored five or six goals and he wasn't wrong.
They looked terrified when the likes of Bojan Miovski ran at them and Aberdeen improved hugely as the game went on with the Swedes wilting and they looked happy to hear the final whistle.
Both Aberdeen goals were high quality efforts. Bojan Miovski took a delicious touch before rattling a fine finish into the net.
And Nicky Devlin took the touch of a more accomplished striker when he brilliantly clipped the ball past the keeper after finding himself in an unusual position from his central defensive role.
DUK WILL COME GOOD
Last season, Cape Verde international striker Duk ripped apart defences in Scotland for fun and exploded onto the scene with 18 goals throughout the campaign which made him joint top scorer with Bojan Miovski.
This term, it's fair to say Duk has yet to really get going yet and that was summed up when he missed a very decent chance for a Dons equaliser just before the break.
Captain Graeme Shinnie set up the chance with a trademark crunching challenge and the ball fell to Duk in front of goal. He had to react quickly and his attempted lob was smothered by Swedish keeper Peter Abrahamsson, but for sure it was the kind of chance that the diminutive hitman would have snapped up last season.
It can be pointed out though that it did take Duk some time to get up to speed last season too and with Aberdeen insisting he won't be sold in this transfer window, he should soon get back to last season's form.
He's too good a player for him not to improve and progress as the campaign goes on. He has yet to score this season and a goal next week at Pittodrie would be the perfect way to kickstart his campaign.
