ROME — Eusebio Di Francesco implored his Roma players to pull off the "unthinkable" against Barcelona.
Roma has an away goal but trails Barcelona 4-1 going into the second leg of their Champions League quarterfinal on Tuesday.
Having reached the last eight for the time in a decade, Roma feels it has nothing to lose against the likes of Lionel Messi and Luis Suarez.
"We have the chance to do something unthinkable, considering that they practically haven't lost — a miracle if you will," Di Francesco said on Monday.
Barcelona is undefeated in the Spanish league and the Champions League. Its only three losses came in both legs of the Spanish Super Cup to Real Madrid in August and to Espanyol in the first leg of the Copa del Rey quarterfinals in January.
"We've got the duty to try," Di Francesco said. "Let's remember the home match against Chelsea but let's also remember that we're facing an armada."
Roma was thoroughly impressive in beating Chelsea 3-0 in the group stage, and can also take inspiration from the last time it hosted Barcelona.
In the 2015-16 group stage, Roma held Barcelona to 1-1 courtesy of Alessandro Florenzi's astonishing equalizer from near the halfway line.
But Barcelona routed Roma 6-1 in the reverse fixture in Spain much like it manhandled the Giallorossi last week at the Camp Nou.
Own goals by Daniele De Rossi and Kostas Manolas plus some sloppy defending that allowed Gerard Pique and Luis Suarez to score left Roma on the verge of elimination.
"Roma has never had a winning mentality — or hasn't had it for very long," said Di Francesco, who was a midfielder on the 2001 Roma squad that won the club's last Serie A title and is in his first season as the team coach.
"We need to build that mentality inside Trigoria (the team's training center) and we've got to do it with facts and not with chitchat."
While Roma is unbeaten at home in the Champions League, six of its seven losses in Serie A have come at the Stadio Olimpico, including a debilitating 2-0 defeat by Fiorentina on Saturday that dropped it to fourth place.
Fortunately for Roma, key midfielder Radja Nainggolan has returned from a thigh injury after missing last week's match in Barcelona.
Turkey winger Cengiz Under, who scored six goals for Roma in February and March, remains questionable due to an injured thigh.
It's been an up-and-down season for Nainggolan, who was punished by Roma for drunken, live Instagram postings on New Year's Eve.
"It's true that I've never won anything but those that know me know that I've always played to win," Nainggolan said. "Sometimes I prefer the toughest road possible. I chose Roma because it's got great fan support and it would be stupendous to win here."
Barcelona, meanwhile, is wary of a Roma response as it looks to reach the semifinals for the first time since its last title in 2015.
Barcelona was eliminated at this stage in the last two years.
"I've been in football a long time and know that extraordinary things can happen in football," Barcelona coach Ernesto Valverde said. "We've got to ensure nothing extraordinary happens tomorrow. We can't take to the field thinking they cannot compete with us. Having too much confidence could cost us dearly."
Barcelona goalkeeper Marc-Andre ter Stegen is also wary not let in a repeat of Florenzi's goal.
"These things are rare," Ter Stegen said. "Maybe the goal made me a bit stronger, but it certainly didn't change my game. That's just part of life and football — things happen that you don't expect."