Barcelona reached the Champions League semifinals for the first time since 2019 but Wednesday's defeat by Borussia Dortmund gave the Catalans cause for concern.
Hansi Flick's side lost their unbeaten start to 2025, falling at the 25th hurdle, and were given a scare in the 3-1 defeat by Dortmund, progressing 5-3 on aggregate after their emphatic first-leg rout.
Barca have been the competition's most entertaining side and for the first time in years are serious contenders to lift the trophy, but their undoing in Germany sapped at their confidence.
"There was not a great atmosphere in the dressing room... it was only when I told them, 'Lads, we're in the semifinals,' that it lifted a bit," said Flick.
Barcelona started well this season before a dismal slump towards the end of 2024 when they lost momentum and belief, before recovering after the winter break.
As quickly as things changed for the better, they can change again for worse, particularly given Barcelona's hectic schedule as they battle for a potential quadruple.
"It will be important to analyse this game, but we've accumulated a lot of matches, and it could be normal (to have a dip)," said Flick.
The visit to Dortmund was their seventh game in a 20-day spell and unfortunately for Flick, this match showed the coach he cannot afford to rest key players.
The German benched midfield maestro Pedri Gonzalez and Barcelona suffered for it, unable to control the game, pushed back by the hosts.
Inigo Martinez was also rested, with Ronald Araujo stepping in, and the Uruguayan had an uncomfortable night, still not finding his footing under Flick after injury.
Gerard Martin is limited at left-back but must play in the next few weeks with Alejandro Balde injured and unlikely to return by the time Barca face Real Madrid in the Copa del Rey final on April 26.
"We were not up to it today, we made mistakes, switched off... Flick told us we had to improve at halftime," admitted defender Jules Kounde.
'HUGE SUCCESS'
Serhou Guirassy could have netted a treble in the first leg but fluffed his lines, so Barcelona can't say they weren't warned this time.
The Guinean striker's three goals gave Barcelona flashbacks to their dark recent history in the Champions League, with the 4-0 defeat at Anfield by Liverpool, and capitulation against Roma coming to mind.
After Guirassy's brace, Ramy Bensebaini's 54th minute own-goal helped ease Barcelona concerns before the forward bagged his third to set up a tense finale.
Despite the defeat, Flick tried his best to see the positives ahead of Barcelona's LaLiga clash with Celta Vigo on Saturday.
"Today we didn't show what we want, we will analyse that – but we have improved this season," said the coach.
"We are still in three competitions. We are in the Champions League semifinals.
"This is a huge success and something we should be very happy about."
Flick's team are attack-focused, steamrolling opponents to mask their defensive frailties, but wingers Raphinha and teenage star Lamine Yamal have lacked spark in recent outings.
That means any mistakes at the back – such as the penalty given away by Wojciech Szczesny, or Araujo's error for Guirassy's third goal – could prove costly.
Barca hold a four-point lead on Real Madrid in LaLiga but still have to face the second-placed champions on May 11, in a match which could decide the title race, as well as in the Copa del Rey final.
And in the Champions League either Inter Milan or Bayern Munich await, ready to exploit the same cracks Dortmund found.