Ajax were up against it.
No team had ever overturned a 2-1 home defeat in Champions League history, and the Amsterdam club hadn't progressed through a knockout tie in 22 years.
Real Madrid stood in their way.
The European champions.
The Spanish giants who had won three Champions Leagues in a row, and had reigned the high seas of Europe for 1,011 consecutive days.
The team who were so confident of progressing that their captain Sergio Ramos picked up a deliberate booking in order to miss the second leg.
Ajax entered the second leg of their last 16 clash knowing they would have to score at least twice to progress to the quarter-finals.
Madrid have struggled this season, but Los Blancos have managed to turn it on when required in Europe for some time.
However, Ajax brought a storm to the Bernabéu, and Dusan Tadic was at the heart of the maelstrom.
Tadic produced the best performance of his career to inspire Erik ten Hag' visitors to an historic victory over Santiago Solari's hosts.
To indicate how good he was, he is only the ninth player to achieve the maximum 10/10 rating in French publication L'Équipe.
The former Southampton winger scored a superb goal and had a hand in two others as Ajax stunned Madrid.
Ajax made the perfect start in the Spanish capital, opening the scoring within seven minutes.
Tadic dispossessed Sergio Reguilon and then had the vision to pull the ball back to the onrushing Hakim Ziyech in the box.
Ziyech produced a fine side-footed finish into the far corner past Thibaut Courtois to fire the Eredivisie side into an early lead.
Just three minutes earlier, Madrid had almost opened the scoring after Raphael Varane's header cannoned back off the crossbar.
However, Ajax made the home side pay shortly afterwards, and doubled their lead in just the 18th minute.
Tadic produced a moment of magic to carve open the Madrid defence.
The 30-year-old danced away from Casemiro with a delightful 'Zidane' turn, before threading a perfect pass through to David Neres.
Neres calmly rounded Courtois and dispatched his finish to put the away side in the driving seat.
Tadic claimed afterwards that he has been watching videos of Zinedine Zidane, and his superb assist was straight out of the former Madrid Galactico's textbook.
Ajax had chances to add to their aggregate advantage, but Courtois made a smart stop from Tadic's low volley, and Neres' chip sailed wide of the far post after another brilliant through ball by the Serbian playmaker.
Things got even worse for Madrid when they lost Vinicius Junior and Lucas Vazquez to injury in close proximity, with Solari turning to Gareth Bale and Marco Asensio to turn the tie around.
Bale struck the outside of the post in the 42nd minute, but Ajax held their two goal advantage as the half-time whistle sounded at a shocked Bernabéu.
Both sides had chances after the restart, with Courtois keeping out a Donny van de Beek effort after another sumptuous Tadic pass.
Bale and Karim Benzema had chances for Madrid, but it was Ajax who scored the crucial third goal.
Noussair Mazraoui just kept the ball in play - a VAR consultation was later required - to start a flowing counter attack which was finished off ruthlessly by Tadic.
The Serbian picked up the ball on the edge of the box and fired an unstoppable strike into the top corner past the diving Courtois.
Asensio pulled one back for Madrid with 20 minutes remaining, his low shot from the edge of the box creeping in off the far post following Reguilon's cross.
Ajax's fourth goal two minutes later immediately killed off any hopes of a Madrid revival.
Lasse Schone's free kick from the left wing eluded everyone in the box, including the poorly positioned Courtois, and dipped under the crossbar to find the far top corner.
It was a sublime strike from the Denmark international - whether he meant it or not - and one which capped off a wonderful night for the away side.Ramos' decision to deliberately miss the game backfired to put it mildly, with his replacement Nacho struggling badly before being dismissed for a second yellow card late in the game.
The final whistle heralded Madrid's heaviest home defeat in a home knockout match in Europe, and completes a miserable week which has also seen the La Liga club crash out of the Copa del Rey and fall 12 points behind rivals Barcelona in the league.
Tadic has now been involved in more Champions League goals than any other player this season, with his tally standing at six goals and three assists thus far.
He often showed flashes of brilliance in England, but struggled to show it consistently during his spell at St. Mary's.
However, he has been a revelation in Holland, and is only the second Ajax player after Jari Litmanen to score six or more Champions League goals in one season for the Dutch club.
The playmaker also became the club's first player to score in four consecutive Champions League games.
Ajax deserved to emerge as the overall victors given their performances over both legs, and will pose a tricky test in the last eight.
This is a team with a good blend of experience and youth, and manager Erik ten Hag has some of the most talented young players from the most revered academy in Europe at his disposal.
A late mistake outside his own box aside, Frenkie De Jong was imperious in the heart of Ajax's midfield, illustrating why Barca have forked out a huge fee for his services.
Ajax will lose their midfield maestro in the summer, but have plenty of other prospects on their books.
De Jong's fellow midfielder van de Beek is only 21, as is Danish striker Kasper Dolberg.
19-year-old captain Matthijs de Ligt - the most recent winner of the Golden Boy award - is regarded as the best defensive prospect in world football, and will also command an enormous fee if he departs Amsterdam.
Mazraoui is 21, while goalkeeper André Onana and Neres are both 22.
Despite regularly losing their best players to top European clubs, the conveyor belt at De Toekomst shows no signs of slowing down.
Ajax is a club steeped in history, doing things the right way.
It is refreshing to see the Dutch giants back among Europe's elite.