3 takeaways from Liverpool's surprise UCL elimination to Atletico Madrid

Atletico Madrid are at their best when they're written off.

Diego Simeone's troops engineered a 4-2 aggregate victory over Liverpool on Wednesday to book their spot in the Champions League quarterfinals. They unexpectedly won 3-2 in the second leg at Anfield.

The home side should've wrapped up the tie in normal time but couldn't pocket the host of close-cut chances that followed Georginio Wijnaldum's first-half header. Roberto Firmino seemed to send Liverpool on their way to the competition's last eight when he scored early in extra time, but Atleti roared back with a Marcos Llorente double and an Alvaro Morata finish in the 121st minute.

Here are three takeaways from an absorbing contest in northwest England.

Dwindling Diego

You'll miss him when he's gone.

Few footballers have played the villain role as successfully as Diego Costa, and his devious dance on the disciplinary tightrope was captivating at Anfield. In the opening 30 minutes alone, he escaped a booking when he threw the ball away before a Liverpool free-kick and offered an apology of startling insincerity after bumping over Wijnaldum.

He touched the ball 19 times in his 55 minutes on the pitch but influenced his team and the home support's mood throughout that time. He did nothing in possession but an awful lot without it, and he understandably kicked water bottles when he was substituted.

Costa wears the scars and wrinkles of fallen fruit at a neglected mountainside apple orchard, but he's only 31. Yet it's clear that being a wind-up merchant is all he has left. Recent reports from the Iberian peninsula claimed Costa opted out of heading training last week because he was wary of committing aerial challenges following surgery on a neck injury, Spanish football expert Alvaro Romeo told "The Totally Football Show." His bite isn't quite the same.

Even if Costa stays at Atletico Madrid for another campaign, his club isn't assured of Champions League football next season while it sits sixth in La Liga. So, this could be the pugnacious striker's swansong at the top of European football, and that's everybody's loss.

Firmino the facilitator finally finishes

There used to be too much attention on how Firmino's goal-scoring exploits didn't match up to his attacking colleagues and striking rivals in England. He scored or assisted 22 goals over the last two Champions League campaigns, so his contributions should have never been doubted.

This term, however, he's been just a facilitator and not a finisher. He had fired one shot on target in his previous six matches across all competitions before Atletico Madrid's visit. He hadn't scored on Merseyside this season.

Then he did finally ripple the net at home in the first few minutes of extra time. The ball kindly bounced onto his right foot after his header glanced off the post, but his head was on a swivel prior to that. He anticipated a quality delivery from Wijnaldum from the right so ensured he stayed in Stefan Savic's blind spot while his movement forced Sime Vrsaljko to decide whether to double up on him or cover Sadio Mane's run behind. The Croatian did neither.

Firmino is a perfect striker for English football. He built up the necessary physicality in the Bundesliga with Hoffenheim and possesses tactical intelligence in droves. But it seems to have gone stale for the Brazilian in Liverpool.

If Klopp signs off on some high-profile summer departures to keep his squad fresh, expect Firmino to be among them. Bayern Munich have been snooping, according to The Guardian's Barry Glendenning.

Simeone will draw praise, and rightly so

He did it his way.

There has been an identity crisis at Atletico Madrid. Thomas Lemar and Joao Felix headline the cast of expensive entertainers to join the club over the past two seasons, but Simeone, the highest-paid manager in world football, was extremely unaccommodating when they arrived. He wouldn't buckle in his approach: Atletico Madrid would continue to block and bully to glean results rather than unleash attackers who had sparkled in the Champions League with the likes of AS Monaco and Benfica.

And his tactical stubbornness didn't function with his new-look squad. Until Wednesday, both last season and this term were blighted by underachievement.

But now, he's added a famous victory in the backyard of arguably the Premier League's greatest-ever team to his curriculum vitae, and it was completely of his own making.

Felix was disappointing for much of this season, but Simeone built up his minutes and his form over recent matches. The Portuguese provided a beautiful no-look pass for Llorente's first goal that will be forgotten amid questions over the goalkeeping of Adrian. Renan Lodi is blossoming as Filipe Luis' replacement and, despite some carelessness with the ball in this game, the development of Thomas Partey is a supreme achievement for Simeone.

The substitution of Costa was a big decision but it was his replacement, former Real Madrid reserve Llorente, who bagged the two crucial goals.

The ruthlessness of Atletico Madrid in extra time was surprising, but maybe it shouldn't be. Maybe Simeone had a plan for his refreshed roster all along; maybe we've been underestimating him.

Maybe writing off Atleti as Champions League contenders would be a fool's errand.