"Greats of Europe" said the Marca sports daily after Atletico hammered Milan 4-1 on Tuesday night -- with two goals from new hero Diego Costa -- to ensure a 5-1 aggregate win and a Champions League quarter-final place for the first time since Simeone played for the club in 1997.

When the Argentine arrived back in the Spanish capital in December 2011, Atletico were an underachieving mid-table side burdened by a huge debt. In his first 17 months in charge Simeone delivered Europa League, European Supercup and Copa del Rey titles.

Despite having to sell Radamel Falcao to Monaco last year for 60 million euros ($83 million) to balance the books, this season Atletico have become serious challengers to perpetual Spanish giants Real Madrid and Barcelona as well as the rest of Europe.

With just 11 games to go in La Liga, Atletico are in front of Barcelona and just three points adrift of leaders Real. They have now won seven and drawn one of their eight Champions League games on their return to the competition for the first time in four years.

Simeone insisted his side will remain "humble" whoever they are paired with in the last eight. But for a club that has in the past excelled in shooting itself in the foot, he has created an extraordinary belief among players and fans alike.

"We have not been in this competition for a few years and we were desperate to make an impression," said Raul Garcia, who scored Atletico's third goal on Tuesday.

"That is what we are doing day by day and we will see how far we can go."

The Calderon crowd could certainly play a big part if the Atletico bandwagon is to roll into the semi-finals. Nearly 50,000 were crammed in the stadium waving red and white flags and drowning out the Champions League music as the teams emerged with a chorus of the club's anthem.

"The fans were incredible," said Simeone. "Things went how we and they wanted them to.

"When we walked out onto the field and saw all the flags, we had the chance to savour an extraordinary football moment."

The star of the show from then on was Diego Costa as the new Spanish international continued his claim to be Vicente del Bosque's primary striking option at the World Cup by scoring twice to take his tally for the campaign to 29 goals in all competitions.

Costa's rise to prominence has mirrored that of his team. The Brazilian-born striker spent the first six months of Simeone's reign on-loan at relegation threaten Rayo Vallecano, one of four loan spells he was farmed out on before returning to strike up a deadly partnership with Falcao last season.

In the Colombian's absence he has moved up another level, becoming the focal point of the team with his aggressive style of play that symbolises Atletico's approach as a group.

"He can still improve. He has great physical and psychological strength and I am sure there is still plenty more to come from him," insisted Simeone.

"His participation with the Spanish national team will help him improve because they have a different style of play and he adapts well to any style.

"He is destined for great things and everything that happens to him is thanks to his humility. No one has gifted him anything, he has done it himself and everything he does has its base in his work rate and desire."