PARIS — They’ve spent millions over the past couple of seasons, had superstars come and go, but one constant at Paris Saint-Germain remains the same, for the time being at least: if Kylian Mbappé finds his rhythm, he can turn the balance of a match in an instant.

As bad as PSG were at Newcastle United in their last Champions League outing, losing 4-1, they sent out a timely reminder on Wednesday of their credentials as they dismantled AC Milan 3-0 in Group F with their young French stars Mbappe, Ousmane Dembélé, Randal Kolo Muani and especially Warren Zaire-Emery at the forefront of this convincing victory.

And once again it was that man, Mbappe, who was protagonist and chief AC Milan irritant. His first-half performance was ominous enough for the Serie A side that even before the players had sat down in the changing room at half time they already had replacement Davide Calabria warming up. If Plan A fails in stopping Mbappe, then try something else — anything, urgently.

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PSG came into this match with three points from their first two matches, AC Milan with two goalless draws — despite having the third most shots in the Champions League over their first two matches. With the group finely poised with Newcastle and Borussia Dortmund also in action on Wednesday evening at St James’ Park, it was a match where one win either way could swing the balance of this group.

But it was one of those nights at the Parc des Princes where you felt it was going to take something monumental from AC Milan to quieten this raucous crowd.

Amid the smoke from the pre-match cacophony of fireworks were two tifos hung from behind both goals. At the Auteuil end was one of the late French actor Jean-Paul Belmondo, a huge PSG fan. He was immortalised as his secret agent character Josselin Beaumont from the film “The Professional,” while at the opposite end of the stadium was the AC Milan devil. The slogan read: “J’Les ai dans le viseur comme Belmondo.” (I have them in my sights like Belmondo).

And it was PSG’s chief marksman Mbappe who delivered the first shot on target as he fired straight at Milan goalkeeper Mike Maignan after 21 minutes. He then had another sighter in the 29th minute as he cut inside off his left wing to flash a shot across goal. But it was the third effort three minutes later where he finetuned his radar and made it count in the 32nd minute, turning the match on its head in favour of PSG.

It was Zaire-Emery who was the catalyst behind the move. His ability to play as a No. 6, No. 8 and No. 10 means he is equally happy dictating transitions from the back, having a dart through midfield, or acting as the pivot in attack. The build-up to Mbappe’s first combined all of these — a little dart through midfield and finding Mbappe on the left. He targeted Milan defender Fikayo Tomori, turned him in circles, and then fired a shot through the defender and into Maignan’s near corner. It was clinical, emphatic and ruthless.

At that stage the only individual in the Parc des Princes to really lay a glove on Mbappe was a first-half pitch invader who evaded security to get a hug off the superstar.

Calabria was less foolhardy than the efforts in the first half, and was happy for Mbappe to twist and turn before making his move in stopping him, but it was his intervention that led to PSG’s second. By this stage PSG had already had a brilliant goal disallowed for a foul from Manuel Ugarte on Milan midfielder Yunus Musah in the build up as Dembele’s brilliant shimmy and strike on the right was ruled out. But the Parisiens only had to wait another five minutes for the pressure to count. A quick corner found Dembele unmarked, and his shot across goal was parried into Muani’s path, who tapped home in the 53rd minute.

Mbappe could have had a second goal in the 81st minute as a sweeping move found him unmarked, but his shot across goal was tipped onto the post by Maignan. PSG did get a deserved third in the 89th minute as Zaire-Emery found space on the right and teed up Kang-In Lee who finished clinically past Maignan.

AC Milan had their moments. Christian Pulisic and Rafael Leão formed a neat pincer movement on the PSG defence at stages in the first-half, with Pulisic’s runs off the right causing Theo Hernández some difficulty, while Leao put one decent effort wide. In the second-half it was Pulisic who hit one well-struck effort straight at Gianluigi Donnarumma — playing his first match against his former side — while Pulisic had space to put in Olivier Giroud on the 49th minute, only for the pass to be overhit and Giroud scrambling an effort into the side-netting.

This chance was enough for the Auteuil end of the stadium to unleash their latest pyrotechnics display, covering that end of the stadium in a haze of red and blue smoke. And despite some hairy moments from Donnarumma in goal, it proved to be impenetrable for AC Milan.

PSG need to back this up in the return fixture back at the San Siro in a fortnight where Donnarumma will be in for a hostile reception and Pulisic will be back in front of the crowd he’s already won over with his superb start in Serie A. Musah did well against PSG, certainly one of AC Milan’s better players, as he played 77 minutes before being replaced — but this was a dominant PSG performance.

For the PSG fans who sang from hours before kick off, throughout the match, and no doubt late into the night, there’s a sense of them willing this group home. Mbappe’s contract is up at the end of the season and despite having his good friend Dembele in the team, and their outstanding young midfielder Zaire-Emery running things with frightening potential aged just 17 years old, there’s a feeling of finiteness here — at least of this iteration of PSG.

The likes of Neymar and Leo Messi failed to bring the Champions League to The City of Light, and now in what could be Mbappe’s swan song season here, there’s desperation to make this one count. This was yet another reminder of what PSG have in Mbappe but also what they may lose at the end of the season and the unfillable void he’d leave behind.