Neymar and Marquinhos set the stage for a thrilling finale to Group H as Manchester United, Paris Saint-Germain and RB Leipzig battle for two spots in the Champions League knockout stages.
Marquinhos' second-half header, moments after he had blocked a low shot from Anthony Martial, was the vital goal surrounded by a Neymar brace that secured PSG a 3-1 win that leaves them tied with two other teams on nine points.
PSG had looked destined for a far more comfortable victory when Neymar volleyed home from a tight angle in the sixth minute and Fred appeared to headbutt Leandro Paredes midway through the first half. But the United midfielder was handed a brief reprieve with a yellow and the hosts were level soon after when Marcus Rashford's shot deflected off Danilo.
Fred would waste his second chance with a careless foul on Ander Herrera, earning himself a second yellow that made it all the more difficult for United to overturn Marquinhos' goal, one which means they now cannot afford defeat to RB Leipzig in next week's decisive round of fixtures. A brilliant third from Neymar on a late counter-attack sealed the deal.
Recap the key talking points from the game below
Tuchel's tactics save the day
Almost as soon as the whistle blew for the second half it seemed apparent that Thomas Tuchel intended to go for the United jugular. No matter how many numbers the hosts sent forward Neymar, Mbappe and Moise Kean would not be tracking back.
At least it seemed like a deliberate ploy. The reasons behind it were not entirely obvious, yes it would theoretically keep United's full-backs from joining the attack but whilst Alex Telles was something of a threat there was not a clear sporting reason why PSG should be so desperate to keep Aaron Wan-Bissaka from defending.
Whatever the logic it proved to be clearly ineffective, having mustered six shots in the first half it was not until the 64th minute that they managed an effort on David De Gea's goal again. By then, however, Tuchel had spotted the problem and was in the process of fixing it.
Withdrawing Kean for reserve left back Mitchell Bakker and adding Ander Herrera to midfield hardly seemed the natural changes when PSG were chasing the game but it worked. Suddenly Neymar and Mbappe's defensive diffidence was no problem as they formed a strike duo with Bakker and Florenzi pushing up high in support.
That tactical change did not bring about Marquinho's header but it helped win the corner from which that goal came, Bakker overlapping Neymar and seeing his low shot superbly saved by De Gea.
Tuchel has been managing under huge pressure this season at PSG and has not necessarily helped his cause on several occasions but this was certainly a victory for which he deserved a sizeable share of the credit.
Rashford stakes place alongside top forwards
Early on at Old Trafford this seemed to be a game where Neymar and Mbappe would reassert their status as one of Europe's finest frontlines. That they did, but this game was a healthy reminder that Marcus Rashford belongs at least in the tier just below PSG's two superstars.
There was a healthy slice of fortune to his goal, if indeed it does ultimately go down as one of his rather than a Danilo own goal, but Rashford earned that luck with his fearless attacking down the right. At a time when United seemed punchdrunk, their No.10 kept demanding the ball, tracking back to quell the impressive Abdou Diallo and darting forward when the chance to counter came his way.
If he does get that goal it should be fair recompense for his excellent combination play with Edinson Cavani early in the second half, darting down the right before calmly spotting that Anthony Martial would have a better angle for his shot if he squared the ball. United's No.9 ought to have done far better than blaze the ball high into the stands.
Red Fred Reception
The great debate over whether consistency should trump common sense may never be solved in much of football officiating but it seemed for a time that we had reached a consistent approach that everyone agreed made sense when it came to off-ball 'headbutts'. If you moved your head towards an opponent you would get a red card.
On occasions that meant treating a brush of the forehead in the general vicinity of an opponent with the same severity as a more full-blooded hit but ultimately, if you are doing something so cynical and stupid, you can have no complaints if you see red.
Certainly that was the case when Nicolas Pepe lashed out at Ezgjan Alioski in a Premier League match between Arsenal and Leeds United. He was swiftly dismissed and greeted with no sympathy whatsoever, his own manager Mikel Arteta saying he had "let down" his team-mates.
Why then, in an incident that was remarkably similar to Pepe's, did Fred only see yellow when he butted at Leandro Paredes? It was a curious decision without any logical explanation nor much immediate precedent. It would seem nonsensical that the power with which the United player moved his head should in any significant way dictate the sanction.
Ultimately PSG had little reason to bemoan Fred's ongoing involvement in the game. The Brazilian had been struggling even before his indiscretion and was as guilty as anyone of letting Neymar escape unmarked for the game's opening goal. After his yellow a quarter into the game he seemed unable to mentally extricate himself from the running battle with Paredes, who relished needling his opponent.
Indeed Ole Gunnar Solskjaer perhaps ought to explain why he did not withdraw Fred sooner, after narrowly escaping a second yellow for stamping on Paredes, when he was not performing well enough to be worth the risk. Instead he found himself chasing a game a man down when Fred did eventually see red, perhaps harsh for a firm tackle on Ander Herrera, but no less than his previous fouls had deserved.
Abdou Diallo: The repurposed center back attacked with impressive pace and purpose from wide on the left, staying high up the pitch when PSG had the ball so that Neymar could dart infield. RATING: 7
Anthony Martial: None of the three chances he spurned were necessarily sitters - their combined expected goals value was 0.52 - but Solskjaer might have expected more than three tame misses where his forward didn't even get his basic technique right. RATING: 3
Danilo: Hardly the most heralded of PSG midfielders but he did his job shrewdly, cutting out attacks and dropping into defense to add ballast against United's frontline. RATING: 7
State of play
A dramatic day in Group H has left three teams in the hunt for two places. RB Leipzig won 4-3 in dramatic fashion away to Istanbul Basaksehir and must beat United to qualify for the last 16. If United get a point they are through by virtue of their head to head record. PSG will qualify with a draw.