It may have been 2am, but Atletico Madrid fans were in no mood to sleep anyway – 15,000 of them showed up at Madrid's Plaza de Neptuno to celebrate Los Colchoneros' thrilling Copa del Rey win.

It was so much more than a win, though. It was their first Copa triumph in 21 years, and to top it off, victory came against their great enemy.

When Real Madrid and Atletico tussled at the former's Santiago Bernabeu home on May 17, 2013, Diego Simeone's side had not beaten their bitter rivals since 1999.

But success for Atletico signalled their return as a major force in Spanish football.

They will lock horns in the Copa again on Thursday in their quarter-final at the Bernabeu, and for many supporters, the build-up will evoke memories of that iconic and feisty encounter.

Overcoming history and financial muscle

Success had already returned to Atletico. They'd won the Europa League and European Super Cup twice apiece over the previous three years.

And even though Atletico eventually finished a commendable third in LaLiga that season – their highest finish since winning the title in 1996 – there was no getting away from the overwhelming sense of pessimism, which had long been the attitude most associated with the club.

No fewer than 25 derbies had passed since Atletico's last win over Los Blancos, and even that was a relatively hollow victory as they'd ultimately be relegated for the first time since 1930.

Atletico weren't trying to kid themselves into believing they possessed the same weapons as Madrid.

"We have an opponent against whom we cannot make mistakes," Simeone said. "When we talk about the chances that Real Madrid or we have in the final, they are better than us, without a doubt."

Even Atletico striker Radamel Falcao noted Madrid as the favourites because of the "budget they have, and the players they have". He had a point.

"But over one game, everything is different," Simeone added.

For Madrid, the gravity of the occasion couldn't be much more different. Expectation rather hope dominated the build-up as Los Blancos had already missed out on the league title and lost in the Champions League semi-finals.

Only the Copa del Rey could salvage some pride for the season – but not even that would have saved Jose Mourinho's job.

The win that sparked a golden era?

Spanish newspaper La Vanguardia dubbed it "Mourinho's last supper". The Copa del Rey showpiece wasn't technically his last game in charge, but it was his last final with Madrid and a match that many Atletico fans will consider to be up their with their most historic wins.

It was thrilling, gruelling, brutal, but certainly not pretty.

In typical Atletico fashion, Simeone's side did everything they could during the early exchanges to get the faces of Madrid. Cristiano Ronaldo – who put Mourinho's side ahead with a 14th-minute header – was a target for a few meaty challenges.

But then Madrid started to return the favour. Ronaldo, too. He clattered Filipe Luis. Raul Albiol let Diego Costa and then Falcao know he was there.

Those two soon combined for the equaliser, however. Falcao's brilliant pass released Costa and his lethal left-footed finish beat Diego Lopez in the Madrid net.

The cards began to fly after half-time, among them a red for Mourinho after protesting a yellow shown to – surprise, surprise – Sergio Ramos.

Madrid dominated, hitting the post twice after also striking it in the first half, but Atletico held on to force extra time, and eight minutes into the additional 30 came the decisive blow.

Koke's right-wing cross to the near post was perfect for Miranda, whose glancing header left the net bulging and Atletico suddenly within touching distance of a famous victory.

Ronaldo's dismissal for kicking out towards Gabi's face made things a little easier once the subsequent touchline brawl settled. The Atletico captain soon followed him for a second booking, but by that point the game was into its fifth minute of stoppage time. Madrid's race was almost run.

A final throw of the dice saw Lopez go up for a last-gasp corner, but Atletico survived and the referee's whistle followed their clearance, sparking bedlam.

Fourteen yellow cards and three reds summed up the bruising nature of the game, though it was Atletico's fight and spirit that came to define it.

Belief takes root

"Mourinho, stay!" came the chants from Atletico fans at full-time.

The Madrid coach was quintessential Mourinho in the aftermath, simultaneously declaring it the worst season of his career while also noting that "for many coaches that would be a good year".

But this was not about Mourinho. No, if anything he was a mere footnote in this tale.

"If you had made the fans an offer in which you'd said: 'we won't win against them for 14 years but when we do, it will be in the Copa final at their stadium, with them scoring first, hitting the post three times and us winning in extra time,' they'd have signed up for that'," Simeone surmised with absolutely surety.

For some – not Atletico fans – this game may have been lost somewhat in the abyss of time given it's nearly 10 years since the occasion.

But that's arguably only the case because of the successes that have come since for Atletico. That Copa triumph was monumental in the moment, but breaking the duopoly of Madrid and Barca in LaLiga – 12 months later and again in 2021 – will be the legacy of Simeone once his chapter as coach ends.

Of course, it's impossible to definitively tie most successes in football to a singular event, one thing that changes the course of history.

But there was clearly a sense of the 2013 Copa victory taking Atletico to another level mentally. They'd finally overcome two great barriers: domestic success and Madrid's derby dominance.

If this glorious era with Simeone is summarised by Atletico upsetting the status quo, then it all leads back to that day.

Nearly 10 years later, Atletico certainly aren't the team they were then, but they'll go into Thursday's duel with belief that took root on the night of May 17, 2013.