Football can be very, very cruel.
Marquinhos and Eric Maxim Choupo-Moting canceled out Mario Pasalic's sumptuous opener to earn a 2-1 win that seemed well out of the reach of Thomas Tuchel's expensive ensemble and sent PSG into the last four for the first time since 1995.
Neymar may have been the most relieved person in Lisbon. The world's most expensive player botched a pair of one-on-one opportunities in the first half, therefore missing as many big chances in 45 minutes as he had in his previous 11 Champions League outings.
Kylian Mbappe, who was on PSG's bench after he suffered an ankle injury during last month's Coupe de France final, couldn't hide his astonishment when Neymar squandered his first chance in the third minute. The Brazilian latched onto a loose ball in the center circle and streamed toward Marco Sportiello's goal while a gang of Atalanta defenders trailed in his wake. But Neymar somehow steered his effort harmlessly wide.
Neymar's inexplicable miss followed a save by Keylor Navas on Papu Gomez, and the Costa Rican goalkeeper's mesh was also threatened by headers from Hans Hateboer, Mattia Caldara, and Berat Djimsiti in the early exchanges. The pre-match forecasts for rampant, breathless attacking play from both sides were bearing fruit, except without a goal.
The wait wasn't long. Possession was slipping away from Duvan Zapata on the edge of the box in the 27th minute, but Presnel Kimpembe's rather hesitant attempt to win the ball resulted in it bouncing off Zapata and dribbling kindly to Pasalic. The Croatian instantly sent a swerving, left-footed effort into the top corner from around 16 yards. Navas stood no chance.
Neymar had a peculiar first half. He regularly terrorized Atalanta's backline with his pace and trickery but, a few minutes before the break, he wasted another huge opening. A panicky, wayward backpass by Hateboer sent Neymar through on goal, but the forward lashed his shot into the stands. He should've hit the target at the very least.
Neymar may have felt a little better when Djimsiti smashed a close-range effort into the side-netting in the 58th minute. Atalanta won two consecutive headers following a set-piece before the ball dropped six yards from PSG's goal, but Djimsiti's volley couldn't engineer a two-goal advantage for the Bergamaschi upstarts.
Paris Saint-Germain needed one of their stars to haul them out of trouble. Mbappe was called off the bench after an hour.
It took 14 minutes for Mbappe to call Sportiello into action. The French forward was flicked through by an intelligent Leandro Paredes pass and had a shot denied by the goalkeeper's boot after outpacing his marker.
Just as concerns over Mbappe's fitness began to dissipate, Navas was forced to withdraw through injury. Deputy 'keeper Sergio Rico was brought on after the three-time Champions League winner tried to soldier on despite his ailment.
The game started to peter out. Shots were scuffed and balls spun out of play. PSG looked beaten.
However, Les Parisiens unexpectedly put themselves back on level terms when substitute Choupo-Moting's cross was poked in front of goal by Neymar, and Marquinhos pushed the ball over the line from three yards. The celebrations were a mixture of jubilation and disbelief. PSG had gleaned 30 minutes of extra time from a seemingly hopeless situation.
But it got even better for PSG. Neymar nudged a ball down Mbappe's preferred left-hand channel, and the young Frenchman's subsequent delivery was prodded home by the unlikely hero, Choupo-Moting.
For once, it wasn't PSG rueing another disastrous Champions League elimination. France's prestigious capital club is 180 minutes from winning the whole competition.