In a decade of trying to get their hands on the biggest prize in European club football since the transformational Qatari takeover, PSG have appeared in the final just once, losing to Bayern Munich in 2020 after the pandemic forced UEFA to innovate with a 'Final Eight' format.
Otherwise it has been regular disappointment heaped upon occasional humiliation, such as last season's exit to Real Madrid in the last 16, when they led 2-0 on aggregate an hour into the second leg.
PSG have spent the close season trying to ensure that this time there is no repeat, and so in came a new coach, a new man in charge of recruitment, and a clutch of new signings.
Most importantly, Mbappe stayed put, turning down Real Madrid in the hope he can lead his hometown club to a first Champions League title.
It looks like an all or nothing gamble for all parties, only increasing the pressure on PSG to deliver in Europe this season, when Lionel Messi and Neymar are still by Mbappe's side.
The early signs for that trio are promising, leaving aside some concerns about Mbappe's attitude in a Ligue 1 game last month and worries about a war of egos between him and Neymar in particular.
- Neymar transformed -
The Brazilian has been a player transformed in recent months, injury concerns and doubts about his motivation cast aside as he has scored nine goals already this season.
Neymar is playing like someone who knows what is at stake this season, both with his club in the Champions League and his country at the World Cup.
The same goes for Messi, who had a poor first year in Paris as he came to terms with leaving Barcelona.
Six games into the domestic league season and PSG are top of the table, unbeaten and have scored 24 goals.
New coach Christophe Galtier has settled immediately and appears far more authoritative than predecessor Mauricio Pochettino -- he has not been afraid to take any of his three superstars off in games if he considers it necessary.
Meanwhile Luis Campos, the club's new football advisor who replaced sacked sporting director Leonardo, has overseen the start of a revolution in the playing squad.
That is particularly the case in midfield, where Portuguese international Vitinha has developed a promising partnership with Marco Verratti, while compatriot Renato Sanches and Spain duo Fabian Ruiz and Carlos Soler have also arrived.
There has been a clear-out of players who were prominent under Pochettino and his predecessor Thomas Tuchel, with Angel di Maria, Idrissa Gueye and Thilo Kehrer all departing.
Georginio Wijnaldum, Ander Herrera, Leandro Paredes and Julian Draxler are among those who have left on loan.
- Worrying lack of defenders -
But the biggest worry in Paris comes from the fact that PSG -– who have just been fined by UEFA again for Financial Fair Play breaches -- could not raise more money in sales.
That prevented them from bringing in a central defender, with a move for Inter Milan's Slovakian international Milan Skriniar failing.
Galtier has installed a three-man central defence, but now has no specialist back-up to the trio of Marquinhos, Presnel Kimpembe and a creaking Sergio Ramos.
"A coach can't always say: 'I'm missing such and such a player in this position'. You have to adapt," said Galtier, who has coached only six matches in the Champions League, all at Lille.
"I understand that there are questions about my legitimacy, especially because at Lille we didn't do well in the Champions League, but that experience will still help me," he told sports daily L'Equipe before the season started.
He will be the fall guy if another European campaign ends in disappointment, but first PSG will be expected to ease through a group also containing Benfica and Maccabi Haifa.
"We have had a good start to the season, we're scoring goals and playing well," Galtier said at the weekend, before warning: "But the Champions League is another level."
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