Champions League holders Liverpool will need to summon another famous European comeback at Anfield next month after they were beaten 1-0 away to Atletico Madrid in their last-16 first leg on Tuesday.
Spain midfielder Saul Niguez struck the only goal of the game in the fourth minute by bundling into the net from close range following a corner, their traditional weapon of choice in recent years.
"This is the result of hard work and what happens when you never stop believing but keep on going," match-winner Saul told reporters.
"We have kept on working even though no-one believes in us and wants to bring us down. I celebrated the goal with so much passion because I was so up for the game, we have been criticised a lot but luckily I was able to help us out."
Liverpool, who have won 25 of 26 Premier League games this season and are on course for a record-smashing title win, missed a series of chances to equalise in the second half, with Mohamed Salah and captain Jordan Henderson coming closest to scoring.
Jurgen Klopp's side play at home to Atletico on March 11 in the return leg at Anfield, where they produced an incredible 4-0 win over Barcelona in last year's semifinal second leg after losing the first match 3-0.
"It was not exactly what should happen but it happened," Klopp told BT Sport afterward. "It was the fight we expected and the atmosphere we expected but I love so many parts of our game. It is only 1-0 down at halftime and the second half we play at our stadium."
Atletico's Wanda Metropolitano stadium was the scene of Liverpool's 2-0 triumph over Tottenham Hotspur in last year's final but they faced a very different type of atmosphere this time around.
Clouds of billowing red smoke greeted the Atletico bus when it arrived at the ground as the home supporters stoked up a scorching atmosphere throughout the game to give their side a lift in the middle of their worst season in recent memory.
"We conceded the goal from the corner, first chance for them, not even a chance. Bit of luck," Liverpool defender Virgil van Dijk told BT Sport after the match. "We had the ball most of the game but unfortunately could not create massive opportunities. We still have another 90 minutes to set it right."
Diego Simeone's men have looked nothing like the sides that reached the 2014 and 2016 Champions League finals and challenged Real Madrid and Barcelona's duopoly of La Liga for most of this campaign. They trail league leaders Real by 13 points.
But on Tuesday they produced a vintage defensive display, sitting deep and barely giving Liverpool any space for their attacking trident of Salah, Roberto Firmino and Sadio Mane to work their usual magic.
"It is the way they play. It is a bit of the Spanish football as well and you have to adapt but we knew it and I feel we handled it pretty well," Van Dijk said.
Mane was fortunate not to be sent off late in the first half after clashing with Sime Vrsaljko while on a yellow card and he was swiftly substituted by Klopp for Divock Origi, who scored the second goal in last year's final.
He caused little disquiet to Atletico's towering defenders, yet Salah should have levelled with a header which went wide of the near post, while Henderson also narrowly missed the target from inside the area later on.