There will be many who argue that the elimination was due to the "Barca disease," which is that, unless they actually win the competition, then it's normally this stage that does them in. Since 2014, they've wilted four times in the last eight.

What knits those painful experiences together is the sight of a talented, ambitious team reaching -- time and again -- for the gear lever, yet failing to get out of first. Ripped apart in Rome. Bullied, badly, in Turin last year. Impotent in 2014 and 2016 defeats to Diego Simeone's Atletico Madrid.

On Tuesday, the side that normally loves to be chased and harried, as they play pass the parcel with the ball and smuggle possession past whosoever tries to run them down, suddenly found that they'd lost their energy and desire for party games.

The same bunch of players, who normally thrive on pressure, who love to see opposition players committing themselves to the press because (A) they won't catch the fast-moving passes, and (B) they'll tired sooner rather than later, well, those players looked bewildered, apathetic at the Stadio Olimpico.

A parenthesis: On this night, in a stadium where naked desire dragged him through the 2009 Champions League final when he was barely 60 percent fit, Andres Iniesta was no worse than any of his colleagues.

Though his presence was fleeting, his imprint upon this competition in general is utterly gigantic; 10 times his diminutive height. A four-time winner of the Champions League, he was deeply influential in each of those final victories against Arsenal, Manchester United (twice) and Juventus.

Iniesta's contract dictates that he has until April 31 each season to inform the club whether he is automatically renewing his deal, or if he wishes to leave. When he left the pitch, close to the end and with the result already evident to anyone, who understands football or human psychology, there was at least that "Hail Mary" chance that someone would score the away goal to put Barcelona through.

But as I saw how disconsolate Iniesta was, it became clear that he walked off fully aware that these might well be the painful last minutes of a great love affair. "It's a possibility," he admitted when someone asked whether this might have been his final European experience with the team he has inspired for so many years.

In purely football terms, it is as heartbreaking as Roma's absolutely admirable tactical, athletic and sporting performance is uplifting. They picked up the thread that was left dangling at the Camp Nou and which read: "This is the path to the semifinals."

I've been at matches like this before. In 2004, Deportivo La Coruna cheekily took the lead at the San Siro before reigning European champions Milan cuffed them 4-1. Throughout the first-leg defeat, though, it was clear the Spaniards were being betrayed by the score. So it was that return game ended in a devastating 4-0 win for Depor.

The only surprise then was the scoreline, not the superiority, and thus it was on Tuesday. Roma deserved so much more last week but fluffed their lines. Six days later, not only did Eusebio Di Francesco have the perfect recipe -- press high, hold a high offside line, squeeze the pitch, challenge Barca to see if their passing was brilliant or simply average -- but his players were utterly convinced that they'd seen wobbly legs in their opponents at the Camp Nou.

They were right. Not only did Roma run all night, they reverted to the kryptonite tactics that, for years, have haunted Barcelona if they are athletically run down or off form: Possession was launched forward and twice brought goals. Nobody -- repeat nobody -- in the Barca ranks attacked the ball properly or attempted to take charge of the situation.

It enabled Edin Dzeko to have one of the five-star performances of his life; by a crazy distance, he was the Man of the Match. But, to his friends and family, he'll surely admit that he can't believe it was so easy.

Everything he wanted to control, he did. Every time he dragged a Barca player with him they looked lost, not to say nervous. The Bosnian striker might have scored four times as Roma's midfield and back line were constantly allowed space and time to launch the ball toward him.

Meanwhile, Barcelona have faced Roma's kind of three-man high press before, many times. Two wide men close down "split" centre-backs and one down the middle stops Sergio Busquets dropping into the middle and turning with the ball whenever Marc-Andre ter Stegen slides it to him.

On this night, however, not only did Barcelona repeatedly kick possession out of defence, they failed to even try to play their trademark "to me-to-you-to-me-to you" passing across the backline. Under pressure, they not only gave the ball up, but tossed away their footballing identity.

It was remarkable to watch. Either their positioning and work rate were awful or they lost the nerve to sew together those lightning fast pass-pass-passes that earn them applause, points and silverware across Spain and Europe.

Iniesta was blunt: "It's really tough. It seems untrue. Very hard to accept. With the advantage we had, we went out because we really did things badly. The Champions League punishes you for that." The veteran's eyes were moist and pink, but he faced up to his responsibilities in a manner that the rest of his teammates should have replicated on the pitch.

"We so wanted to win this tournament but we've failed to do so again," he added. "We are all in pain -- this will be hard to digest -- but there's nothing for it but that and we've got a big game against Valencia on the weekend and two trophies still to win."

And therein lies the rub. I've written before that five consecutive appearances in the final of the Copa Del Rey have become pyrrhic for Barca. They compete like caged animals throughout January and part of February because that's what they're like, yet they've never learned the habit of taking their foot off the gas... until they finally run out.

The bill needs paying now and Ernesto Valverde needs to examine his learning lessons. He'll win the first Spanish title of his career and, feasibly, also lift the Copa. However, his insistence to not rotate fully, the inability to properly trust certain players and the avoidance of risk when it came to dropping points in La Liga has eventually cost him in a tournament that Barca might have won.

And so to that first point: Those who say "it's the quarterfinal; they always trip up" aren't quite saying enough.

Barcelona were outplayed, they were flat on energy and Roma were excellent in thought and deed. But to lift the great prizes -- particularly to win a Treble -- you need to draw upon reserves of gutsy, aggressive, competitive spirit. Normally this group has gallons of that with which to garnish their talent.

This time, however, they came up empty and the better team won. By a distance.