Substitute Gonzalez Fran added the fourth and AC Milan—who were already trailing on away goals—were sent tumbling out of the Champions League.
A 4-1 win at the San Siro looked good enough, but their trip to Deportivo la Coruna's Riazor proved that anything is possible in football.
Walter Pandiani got the ball rolling on a memorable night in Galicia—particularly given Depor's failings now—before Juan Carlos Valeron, Albert Luque and the Fran completed the comeback back in April 2004.
It will serve as inspiration for Real Madrid, who boast riches that Depor team could only dream of, ahead of Tuesday night's return leg against Borussia Dortmund.
The Germans, who won 4-1 at home last week, will heed it as a warning of what can happen in the Champions League—Inter Milan's comeback against Tottenham in the Europa League this season, even though they still lost, may also act as a precedent for Jurgen Klopp's men to avoid.
To turn it around, Los Blancos won't just have to beat the only unbeaten team left in the competition, they'll have to beat them by scoring at least three goals.
If Real Madrid want to orchestrate a famous night in the Santiago Bernabeu they'll have to be quick out of the blocks, doing as much damage as possible in the opening hour to give themselves a chance of reawakening their La Decima dream.
Angel Di Maria didn't start at the Wetfalenstadion, and his role will be important. The Argentinian adds pace and a direct attacking threat on the right, which balances out with Cristiano Ronaldo on the left.
He was the key as Real beat Atletico on Saturday and played a part in their three best chances—his free kick led to the first goal, he scored the second and a driving run created a great opportunity for Karim Benzema.
In Germany, with Mesut Ozil in that role, Madrid weren't as effective.
Die Schwarzgelben wouldn't consider their defense a weakness, but they're not unbreachable. They've conceded 20 in their 16 away matches in the Bundesliga and six in their five Champions League games outside of Germany (four draws and a win).
What will happen?
Mats Hummels' mistake let Los Blancos in for what may yet prove a valuable away goal last week—any defensive errors in the first half would breathe confidence into Madrid and life into the tie.
As well as the likely return of Di Maria to the starting 11, Alvaro Arbeloa should start too, allowing Sergio Ramos to move back to the center of defense.
With Ramos and Ozil restored to their regular positions, Di Maria testing Marcel Schmelzer and Cristiano Ronaldo rested from the Madrid derby, the game will have to be won through Madrid's fast and incisive attacking.
Jose Mourinho's favored 11 may prove enough to win the match, ending Dortmund's unbeaten run in the competition, whether it will have the legs to win on aggregate though is a different question altogether.