That night still gives Barcelona players cold sweats.
Defeat in Rome was a season-crusher, a catastrophe, a stain on the club which grew only deeper as rivals Real Madrid stormed to their third Champions League victory in three years.
Barcelona headed to the Italian capital last April with a 4-1 lead from the first leg, one foot in the semi-final. They left with their tails between their legs after a crushing 3-0 defeat which inflicted a deep cut on the club’s soul.
One which is still healing, and perhaps only lifting the trophy will finally remedy it. It is Barcelona’s prime objective this season, something the Catalans have made no secret of.
Lionel Messi’s speech at their curtain raiser friendly at Camp Nou in August showed how much the Barcelona skipper – and by extension, the club – wants to win the Champions League.
The key to that locked door is Ousmane Dembele.
Valverde sat the Frenchman on the bench last season in Rome, even though his attributes would have been perfect to help Barcelona hit the hosts on the break as they attacked with abandon to try and make back the aggregate score.
Dembele was eventually called upon in the 85th minute, but it was far too late for him to rescue the Blaugrana, with Kostas Manolas’s crucial third goal dumping them out.
In mitigation for Valverde, Dembele was not the same player he is now.
Injuries suffocated his debut season, the former Borussia Dortmund star struggled for both form and fitness, with inconsistent displays and struggles to adapt to life at the club meaning the coach could not rely upon him.
Nearly a year on, Dembele has finally turned the page and as Barcelona head to his native France to face Olympique Lyonnais on Tuesday, their €147 million weapon is ready to detonate.
On a personal level it is also an opportunity for him to set a few things straight.
In France Dembele is viewed through the prism of his controversies, those are the stories which make it into the public eye back home.
The winger has not earned a starting berth in the national team, only participating in brief cameos during the World Cup in Russia. Without shining in a ‘big’ game for Barcelona either, his successes have gone under the radar.
His position on the scale between clown and genius is still being debated in France.
Barcelona fans, though, fully appreciate the transformation Dembele has gone through and how vital he has become.
From being touted for the transfer list, the forward is now a crucial cog in Barca’s attack. In the last few weeks following an untimely ankle sprain, the team has faltered without him.
Philippe Coutinho has been filling in on the left flank but offers none of the speed or skill which Dembele combines so effectively.
On Saturday against Real Valladolid, Dembele started for the first time since that set-back and showed flashes of his best before being taken off to rest for Tuesday.
“At times we’re on the counter and I can’t get there in time!” Luis Suarez told Diario Sport.
“I’m not able to get there and Leo is even further behind [Dembele]. We say ‘he goes really fast, we’ll never catch him!’
“When he starts to run, we need to start further ahead of him to be there at the right time. If not, it’s impossible to keep up.”
The Uruguayan can joke away, but having a player who is so speedy is a big boon for him and Messi, the same way Neymar was before his move to Paris Saint-Germain.
What’s pleasing for Barcelona is that the conversation around Dembele now purely concerns his quality and not his unprofessional habits.
Suarez was one of a few team-mates to publicly rebuke Dembele earlier in the season, telling him to be more responsible.
Late nights, chowing down on junk food and poor timekeeping threatened to derail his season after a promising start.
But Dembele has cleaned up his act. He is training well now, with a good attitude. Nelson Semedo and Valverde have attested to that fact. And the only thing left for Dembele to do is produce in games which matter.
His last gasp equaliser against Atletico Madrid at the Wanda Metropolitano at the end of November was the first step in the right direction.
“I had a spell on the bench, but that’s normal because during a season there are always difficult moments,” said Dembele, who knows exactly what he must produce, and when.
“I have faith in myself and I will keep trying to do what I know how, and to be decisive. It’s important to score in key moments.”
The first in a series of those is fast approaching as Champions League-chasing Barcelona head to Lyon.