The unthinkable almost happened again. After Barcelona let a 4-1 first-leg lead slip away to Roma on Tuesday to crash out of the Champions League in humiliating fashion, Real Madrid almost followed them with an even worse capitulation on Wednesday.
Zinedine Zidane's side had thrashed Juventus 3-0 in Turin and looked likely to cruise into the semi-finals in a home leg that appeared a formality, almost a dead rubber. But if Tuesday night's action showed us anything, it is that these ties are far from over at the halfway stage.
Like Barca and also Liverpool against City on Tuesday, Madrid conceded an early goal as Mario Mandzukic converted inside a minute and a half. And the Croatia striker scored again before half-time to make the home fans very nervous indeed.
That is how quickly a tie can turn on its head in the Champions League and, suddenly, the defending champions were running the risk of catastrophe against a Juve side with absolutely nothing to lose.
This was reminiscent of Madrid's Dortmund defeat en route to the 2014 Champions League crown, when Carlo Ancelotti's side lost 2-0 in Germany after winning the first match 3-0 in Madrid.
On that night, a young Casemiro was the unlikely hero with a spirited showing in central midfield. In this match, however, the Brazilian was withdrawn at half-time along with Gareth Bale as Zidane threw the dice, Lucas Vazquez and Marco Asensio coming on in their place.
Bale failed to impress in attack, but he is not a centre-forward and the decision backfired, while the young Jesus Vallejo was given a baptism of fire at centre-back in his first Champions League appearance as he started due to the absence of skipper Sergio Ramos (suspended) and Nacho (injured).
And things got worse for Madrid before they got better as Blaise Matuidi levelled the tie at 3-3 following a howler from Keylor Navas, the Costa Rica goalkeeper spilling the ball just yards from goal.
There was still half an hour left and Madrid were on the verge of one of the most embarrassing nights in their history. With disaster impending, it was a good time to finally find focus.
At 3-3 on aggregate, Real pushed and Juve began to look tired. Theirs had been a monumental effort and just when it seemed as if the night was heading for 30 more minutes of drama in the shape of extra time, Madrid won a penalty after Medhi Benatia appeared to shove Lucas Vazquez in the back.
Juve's players protested vociferously and Gianluigi Buffon was shown the red card in what may well have been his final Champions League game, the 40-year-old applauded off the pitch by both sets of fans.
And as so often, it was left to Ronaldo to have the last say, the Portuguese blasting the penalty into the top corner to break brave Juve's hearts and get Real Madrid out of jail as they progress, by the skin of their teeth, to the last four of the competition.
So Los Blancos won the tie in the end, but as they seek a third straight European Cup crown, they definitely lost their fear factor against Juve on Wednesday night.