Champions League holders Liverpool crashed out in the last 16 on Wednesday after a stunning fightback from Atletico Madrid sealed a 3-2 win on the night and a 4-2 aggregate success.
Here are three things we learned from Liverpool's unexpected exit:
For much of this season, Liverpool had looked like an unstoppable juggernaut as they powered towards the Premier League title and a potentially successful defence of the Champions League.
But in the space of just three weeks, Jurgen Klopp's team have unexpectedly lost their way and the slump has shattered their bid for a seventh European Cup and an unbeaten Premier League campaign.
When Liverpool arrived in Madrid for the first leg on February 18, they were on the crest of a wave.
But a limp 1-0 defeat there was an unsettling glimpse of what was to come as the Reds' run of 18 successive Premier League wins was ended by lowly Watford in a stunning 3-0 defeat.
A 2-0 FA Cup fifth round defeat at Chelsea would be partially excused by Klopp sending out a slightly weakened team.
Liverpool still looked shaky in a narrow 2-1 success against struggling Bournemouth on Saturday, yet they should have been out of sight before Atletico authored their incredible comeback.
The hosts had 26 shots in the first 90 minutes but could only manage one goal from Georginio Wijnaldum thanks to their poor finishing and the inspired form of Atletico keeper Jan Oblak.
That forced extra time and when Roberto Firmino scored his first Anfield goal of the season Liverpool were 2-1 up on aggregate.
Yet Adrian's mistake was punished by Marcos Llorente to give the Spaniards hope and Llorente netted again before Alvaro Morata capped the epic collapse.
Liverpool will still win the title but the shock on Klopp's face was clear to see.
Just 167 seconds after Roberto Firmino appeared to have put Liverpool on course for the quarter-finals, Adrian's howler gave Atletico a lifeline that turned the tie on its head.
The Liverpool goalkeeper made a total hash of a routine kick downfield and booted the ball straight to Joao Felix.
Atletico striker Felix picked out Llorente and he cut inside to fire back past Adrian.
It was a hammer blow that Liverpool could not recover from, underlining just how much Klopp's side missed the injured Alisson Becker.
Adrian, 33, has been guilty of other errors this season when he has stood in for Alisson this term and once again he fluffed his lines.
Alisson is sidelined with a hip injury suffered in training prior to Liverpool's FA Cup defeat at Chelsea and former West Ham keeper Adrian was guilty of allowing Willian's shot to slip through his grasp into the net in that clash.
While Liverpool look certain to win the Premier League regardless of who is in goal, Alisson is not expected back in the short term, giving Klopp a headache as he considers whether to keep faith with Adrian.
With sport across the world thrown into chaos by the coronavirus, Liverpool were bucking the current trend for playing behind closed doors, but their supporters might have wished the game had been part of the fan ban as the Reds crashed to a stunning exit.
Fears about the growing spread of the deadly virus have prompted sports governing bodies to cancel matches and tournaments.
Football matches in several European countries have been played in empty stadiums as authorities limit large public gatherings and Paris Saint-Germain beat Borussia Dortmund in a deserted Parc des Princes in their last 16 second leg on Wednesday.
Many Europa League ties scheduled for Thursday are due to be played in closed grounds, but Liverpool were given the all-clear to open the gates for Atletico's visit and 54,000 crammed into the famous old arena.
Aside from Liverpool manager Jurgen Klopp and Atletico boss Diego Simeone exchanging a shoulder bump instead of a handshake before kick-off and players from both teams not shaking hands, as per the virus guidelines, the alarming outbreak was put to one side as fans focused on a classic European tie.