Paris Saint-Germain's unbeaten European record fell at the Etihad Stadium, with Mauricio Pochettino's side conceding twice in the final half-hour to lose 2-1 to Manchester City.
Kylian Mbappe had given the visitors the lead early in the second half, but Raheem Sterling equalised from close range before Gabriel Jesus completed the turnaround.
The result means City will finish top of their Champions League group, with PSG forced to settle for a runner-up spot and a potentially tougher last-16 draw when the tournament moves into the knockout stages.
The French side's expensively-assembled front three were unable to lead them to victory in Manchester, and defender Presnel Kimpembe hinted that the defensive contributions of Mbappe, Neymar and Lionel Messi - or lack thereof - played a part.
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In the aftermath of the game, PSG's lack of balance was cited as a reason why their efforts to win their first Champions League could once again come up short.
The addition of Messi to an already stacked front line has helped Mauricio Pochettino's side dominate domestically, but pundits felt as though it caused issues in Europe.
"If you want to win the Champions League, you cannot defend with seven players," Thierry Henry said, while Jamie Carragher argued "I would be gone tomorrow [if I was Pochettino] and it's because of those 3 stars."
Kimpembe said after the game that "We know we can do better," before acknowledging everyone in the side needs to work together if PSG are to avoid repeats of the City loss.
"We are competitors and we don't like defeat. What do we have to improve on? We have to kill the games earlier.
"We also have to work as a team, middle block, sliding, and that will do the trick."
PSG are assured of a place in the last 16 of the Champions League for a 10th straight year, thanks to RB Leipzig's victory over Club Brugge in the group's other game.
However, they are still yet to win the competition, and have only made the final once, losing to Bayern Munich in 2020.
Last season, Pochettino's side reached the semi-finals of the competition but lost both legs of their meeting with Guardiola's City side.
After the midweek defeat, manager Pochettino evaded questions about his future in the French capital.
The Argentine has been heavily linked with the vacant manager's position at Manchester United, with pundit Henry suggesting "Pochettino cannot be Pochettino at times" with the current PSG team.
PSG will round off their group stage campaign in December with a match at home to a Club Brugge side who held them to a 1-1 draw in the reverse fixture., with their preparations coming against the backdrop of Zinedine Zidane being mentioned as a potential successor to the current manager.