The former Borussia Dortmund coach has eight days to prove his worth to the club’s board. Quite simply, that means picking up a minimum of four points in clashes against RB Leipzig and Manchester United.
Anything short of that tally will likely see PSG consigned to the Europa League after Christmas, by which time it would be a miracle if Tuchel was still in charge.
Having hit the club's European high point in August, this would make a dramatic low; the first time in the QSI era that last-16 qualification would not be attained.
The Parisians lead Ligue 1 on 24 points, but a log jam of teams hover in close proximity. If Marseille win their two games in hand, they can draw level with the Parc des Princes club, who have lost more domestic fixtures this season than Lille, Lyon and Lens to name a few.
On Friday, they led 2-0 in Monaco but crumbled embarrassingly in the second half to lose 3-2. Their inability to react to the game slipping away from them echoed the manner in which they lost control in Leipzig in the Champions League at the start of the month and was arguably even more worrying than the outcome of the game.
But it is not their domestic form, necessarily, that is causing consternation. On the continent, in a group that was considered to be relatively clement, PSG are ailing.
They have produced three lacklustre performances that have yielded three points. Defeats against Manchester United and Leipzig have put them on the precipice.
It is true that injuries and illness have contrived to test them. It is also true that the squad that has been left to Tuchel has gaping holes which were not evident a year ago. But it is equally true that they have underperformed to a grave level.
Tuesday’s match in the French capital, then, promises to be a nervy affair.
The levels of concern that PSG are suffering ahead of the clash have been made evident by the coach’s very public stance on Neymar’s lack of fitness. It is clear the Brazilian is not primed for such an encounter, but such is the desperation of the hour, he is required.
“We need him. It’s absolutely necessary that he plays,” he told the press. “He has the confidence, the quality and the experience. He is a key player for his team.
“He’s not in the best physical state, but he will start tomorrow. He can physically and mentally handle this kind of match.
“I hope that it’s not too much for him and that we will help him. We must work for him. He is not alone.”
Never the most industrious of characters in a defensive sense, PSG are ready and willing to go shorthanded at the back to allow the 28-year-old the luxury of focusing on his offensive game.
That Neymar is “necessary” for PSG does not only reflect on his individual quality, though. It shines a light on both PSG’s failed summer transfer window and the one-dimensional nature of their side, which leans on both the former Barcelona forward and superstar sidekick Kylian Mbappe in attack.
Indeed, the club’s Champions League struggles can be traced back directly to this pair, who have not found the net on a single occasion in the competition this season.
“If Kylian and Ney don’t score, it has a big impact on us because they are decisive players,” the coach admitted. “We need goals from them and great performances.”
Unfortunately for PSG, neither is at full capacity ahead of the clash. Furthermore, there are still worries over midfielders Marco Verratti and Ander Herrera, as well as forward Mauro Icardi, who has barely played this year.
Throw in injuries for Juan Bernat and Thilo Kehrer in defence, and suspensions for Presnel Kimpembe and Idrissa Gueye, and this is a full-blown selection crisis.
During the Final 8 in Lisbon, PSG were able to rally around as a team to overcome such difficulties.
On Tuesday, the focus will revert to the superstar pairing. Tuchel and PSG are staking their reputation on them.
“You don’t get to a Champions League final by clicking your fingers,” Marquinhos said on the eve of this clash.
Equally, though, you don’t get to the showpiece with performances like PSG have produced so far. After the wretched display in Germany at the start of the month, the coach said he did not fear for his job.
“If we win at the Parc, the situation is totally the opposite,” he noted.
With an uneasy relationship with sporting director Leonardo, anything but victory could be the beginning of the end.