Dortmund came into this encounter in good form, having lost just once in the Bundesliga all season.
However, their two-goal buffer in the tie was halved within five minutes in Bergamo. Nicola Zalewski had already drawn a brilliant save from Gregor Kobel by the time Lorenzo Bernasconi’s cross was turned into Gianluca Scamacca’s path by Ramy Bensebaini, allowing the Italian centre-forward to tap home.
The hosts continued to cause their opponents problems, and Zalewski was a constant threat; the Poland international drew another desperate stop from Kobel before curling over the bar from just outside the area.
Shortly before the half-hour mark, Die Schwarzgelben grew into the game and had a couple of chances of their own. Serhou Guirassy headed off-target at the back post, but Marco Carnesecchi was alert to keep out Julian Brandt’s snapshot.
Nevertheless, the visitors found themselves two behind on the night on the brink of HT, benefitting from a slice of fortune as Davide Zappacosta’s shot deflected off Bensebaini to evade Kobel on its way into the back of the net.
After the restart, the game was more balanced, with both sides having chances as Mario Pašalić fired at Kobel inside the area, shortly before Maximilian Beier, bearing down on goal and with only the goalkeeper to beat, struck the post from a tight angle.
Within minutes, the away team were made to pay for their wastefulness as Atalanta netted a third to move ahead in the tie. On this occasion, Pašalić picked his spot with a glancing header from Marten de Roon’s inswinging cross, sending the home crowd into raptures.
In response, Niko Kovač made four substitutions in the space of 10 minutes, and after Guirassy had miskicked the ball with the goal at his mercy, two of those replacements combined to level the tie.
Karim Adeyemi played a quick one-two with Carney Chukwuemeka before curling into the top corner on his left foot, setting up an enthralling final quarter-hour.
Just as ET seemed inevitable, a controversial moment decided the encounter late on. Kobel, who had been excellent throughout, lost the ball outside of his area, allowing Atalanta to launch one last attack.
The Swiss shot-stopper then got a fingertip to Pašalić’s lobbed pass, which only directed it into the path of Nikola Krstović, and although Bensebaini did clear the ball for the corner, he caught the striker’s head with his boot in the follow-through.
Following a VAR intervention, a penalty was awarded, and a red card to Bensabaini was dished out, allowing Lazar Samardžić to convert from the spot with the last kick of the game.
Dortmund’s exit could not have been more dramatic, with Nico Schlotterbeck also seeing a red card brandished while on the bench, but they only have themselves to blame for allowing a comfortable first-leg win to slip through their fingers.
Atalanta, though, bring an an end to a three-game losing UCL streak in style, and can now look forward to Friday’s draw to find out if they face Bayern Munich or Arsenal next.
Flashscore Man of the Match: Mario Pasalic (Atalanta BC)