Paris Saint-Germain have suffered heartbreak in the Champions League before. But on Wednesday, they inflicted it.

Down 1-0 until the very last minute of regular time, PSG scored twice in quick succession to beat Atalanta 2-1 in their quarterfinal tilt. Goals from Marquinhos and substitute Eric Maxim Choupo-Moting sent PSG to the Champions League semifinals for just the second time in club history and ended Atalanta’s remarkable run in Europe.

Here’s what we learned from an unbelievable night in Lisbon:

PSG’s stars inspire comeback

Neymar was PSG’s only threat for large parts of the match. Though he missed some significant chances – including a clear breakaway against helpless ‘keeper Marco Sportiello early in the contest – Neymar was at least pulling his weight. Without the injured Marco Verratti, PSG’s midfield did little to move the play forward or create chances for the front three. Mauro Icardi was marooned on an island up front, Pablo Sarabia was unable to get involved, and Neymar was left alone to dribble through the entire team.

The Brazilian, incredibly, finished the game with 16 successful dribbles, the most in a single Champions League match since that stat has been recorded.

Eventually, he got some help.

The game changed when Kylian Mbappe stepped onto the pitch. The 21-year-old, who recovered in time from a tricky ankle injury, put tons of pressure on Atalanta’s creaking backline. Already tired from a physical match, the defenders struggled to keep up with Mbappe’s darting runs.

Neymar continued to cause chaos in and around the penalty area and ultimately provided the assist for the equalizer.

But PSG’s comeback was less by design and more out of desperation. Atalanta tried to nullify PSG with their physical play, and forced the game to a halt on several occasions. With 29 fouls and six yellow cards, Gian Piero Gasperini’s side did its best to slow down PSG’s most talented players. It just wasn’t enough.

Atalanta’s lack of depth shows

It’s no coincidence Atalanta lost this game in the second half. They simply don’t have the depth to compete with the game’s deepest – and richest – teams.

Even without Verratti and the suspended Angel Di Maria, PSG manager Thomas Tuchel could call upon Julian Draxler and Leandro Paredes off the bench. Gasperini had no choice but to throw on 19-year-old youth product Jacopo Da Riva, who came into the match with just a single minute of Serie A experience under his belt.

Atalanta were already without Josip Ilicic and starting ‘keeper Pierluigi Gollini, increasing the chances of a potential burnout. You could see the fatigue in the final minutes of the game. It’s unbelievable Atalanta were able to play with intensity for as long as they did. Marten De Roon produced a fantastic tackle on Neymar in the 76th minute, and his teammates consistently won duels in the air and on the ground. But PSG kept the pressure on, moving the ball from side to side, and Atalanta eventually cracked.

Tuchel can’t be satisfied

The look on Tuchel’s face said everything. He was ecstatic, screaming into the night like the rest of his players, and rightfully so. Comebacks don’t happen often, and they hardly happen that late in the game. But his team didn’t play well. Despite all the possession and the attempts on goal, PSG lacked the precision and the purpose that they’ll need in the semifinals against either RB Leipzig and Atletico Madrid, two clubs that also play at a high tempo.

PSG struggled against Atalanta’s press, and when they broke it, they couldn’t capitalize. The serial Ligue 1 champions didn’t play like a team. Verratti’s absence certainly had something to do with it. The Italian is often the link between midfield and attack, and he’s the kind of player to both win possession and create chances. Marquinhos, Ander Herrera, and Idrissa Gueye – all on the defensive side of the midfield spectrum – just couldn’t figure it out, forcing Neymar and Mbappe to create chances on their own.

They also have to find a way to get the ball to Icardi. He needs service to make a difference, or he might as well not play at all. Icardi managed just 21 touches before coming off in the 79th minute. Only one of them was in the penalty area.

PSG will need a more collective effort in the semifinals to ensure Wednesday’s dramatic comeback wasn’t in vain.