Roma's Daniele De Rossi and Alessandro Florenzi celebrated a remarkable win over Barcelona

Liverpool fans are going into this week's Champions League semi-final first leg with Roma in confident form - but are the Italian capital side being underestimated?

After all, they have already completed one of the all-time great European fightbacks to reach this stage.

As Roma manager Eusebio di Francesco walked into the media room at the Stadio Olimpico after stunning Barcelona, the local press pack applauded.

They couldn't believe what they had just witnessed. Il Corriere della Sera's headline writer called it La Grande Bellezza - The Great Beauty - name-checking Paolo Sorrentino's Oscar-winning film about life in the Italian capital.

In strictly footballing terms, you have to say Roma's performance and comeback against Barcelona - which set up the semi-final against Liverpool - also merited an award.

"We reached perfection," midfielder Radja Nainggolan said afterwards.

Anything less would not have been enough. Only two teams had ever come back from a first-leg deficit of three or more goals in the Champions League era. One was Deportivo La Coruna against AC Milan in 2004. The other was Barcelona against Paris St-Germain last season.

It's worth putting what Roma achieved two weeks ago - against a team they lost to 6-1 in 2015 - into some perspective.

Five-time Ballon d'Or winner Lionel Messi, supposedly unfit, scored a hat-trick in the previous week's 3-1 win against Leganes. That result meant Barcelona matched the La Liga 38-game unbeaten record established by Real Sociedad between April 1979 and May 1980. They have since broken it - on 40 games and counting - and beat Sevilla 5-0 in the Copa del Rey final.

The Catalans haven't been bad in Europe either. They travelled to Rome with the best defensive record in the competition. Barca had shipped just three goals in nine games - the same number Roma needed in 90 minutes.

Is it any wonder that Pierluigi Pardo, the commentator for Italian broadcaster Mediaset, opened his commentary with the line: "Roma have got to climb Everest"?

Football Focus: Edin Dzeko reveals Champions League texts to former team-mate Mo Salah

A sense of destiny?

"I saw that people were giving us just a 5% chance to go through," striker Edin Dzeko observed.

But it was seeing the number of people who turned out at the Olimpico that made Roma's captain Daniele de Rossi believe the impossible was actually possible.

"I was almost moved [to tears] seeing the ground full. The people believed in us. I told my team-mates that if they believed, we should too," he said.

Roma have constantly been underestimated in the Champions League this season. No one expected them to get out of a group including English champions Chelsea and Atletico Madrid, finalists in 2014 and 2016.

But they topped it. OK, the Giallorossi have had a bit of luck along the way: were it not for Bruno Peres' big toe stopping a 2-1 loss to Shakhtar Donetsk becoming 3-1 in the final seconds of the last-16 first leg in Kharkiv, maybe Roma wouldn't be here now.

Then again, after coming back from an even bigger deficit against Barcelona, who can say?

There is a sense of destiny about this team. Dzeko opened the scoring against Barca and now has more goals for Roma than Rudi Voller.

He could have joined Chelsea in January but chose not to. De Rossi and Kostas Manolas got the other goals and it was incredibly poignant that they did after the own goals they scored at the Nou Camp.

Manolas couldn't believe it and sat crying in the dugout after the full-time whistle. It sent the red and yellow side of the city into delirium.

Roma's owner Jim Pallotta dived into the fountain in Piazza del Popolo as if he were Anita Ekberg in La Dolce Vita. The city didn't sleep.

'I must be a madman'

Roma's average position against Barcelona (left) shows how high they pressed

Di Francesco didn't sleep the Saturday before the game either. He was up until 5am working on how to make Roma better in front of goal, identifying where exactly they could hurt Barcelona.

He watched Chelsea's tie against them and, after playing 4-3-3 all season long, decided to switch to 3-4-3.

"I must be a madman," Di Francesco said, "because when a coach does something like that he takes a big risk. You would have killed me [if it hadn't worked]."

The story Di Francesco told is instructive for a number of reasons. First of all, it highlights his dedication and meticulousness.

Take this as another example. If Messi had a free-kick in the inside-right channel, Federico Fazio positioned himself as the third man in the wall. On the other hand if the Argentine had a free-kick in the inside-left channel, his compatriot Fazio became Roma's first man. The attention to detail Di Francesco goes into is something else.

Then there's the courage to change system with just two days to prepare. Although the formation was different, the philosophy remained the same: squeeze the life out of your opponent.

Roma have one of the most co-ordinated and effective pressing games in Europe. The Wolves, as Roma are known, hunt in packs.

Sergi Busquets and Andres Iniesta couldn't get the ball in the second leg. Barcelona's top two passing combinations were as follows: right-back Nelson Semedo to central defender Gerard Pique (19 times) and Pique to goalkeeper Marc-Andre ter Stegen (12 times).

More than half of the German keeper's passes were long and everybody knows how much Barca love to pass it out from the back.

"I've never seen Barca put in such difficulty," Dzeko said.

Ter Stegen's opposite number Alisson - arguably the best in the world this season along with Manchester United's David de Gea - did not have a big save to make all night. Roma have kept clean sheets in every home Champions League game this season. That's despite coming up against Messi, Luis Suarez, Antoine Griezmann and Eden Hazard.

'We will join our spirit with theirs'

The next test of course is Liverpool and a certain Mohamed Salah, sold to the Anfield club for £34m in the summer and scorer of 41 goals in 46 games since then. For Roma to reach a European Cup semi-final for the first time in 34 years - since they lost to Liverpool in the final - after losing a player like him makes the job Di Francesco and the club have done all the more remarkable.

Salah helped Dzeko become Serie A top scorer last season. He is remembered with great fondness at the club. It'll be tough to stop him but Alisson, Manolas and Fazio know him better than any backline in the world.

"Liverpool's exploits are like ours," De Rossi said after the draw. "They beat the team I thought were the favourites. They have a coach I am crazy about.

"Whoever we ended up drawing it would have changed little. That's the level we're at now. All the teams left in the competition are strong."

And yet Roma believe.

"I am sure that, deep down, this tie was the one in the hearts of all Roma supporters," Di Francesco said.

"Once again, we will join our spirit with theirs - and take on this semi-final with the same determination and pride that has got us this far."

A version of this feature was first published on 13 April