PARIS — Three thoughts from the Parc des Princes as Paris Saint-Germain enjoyed a stunning 4-0 victory over Barcelona in their Champions League round of 16 first leg.

1. Blistering PSG blow Barca away

After so many false dawns in the Champions League, could this be Paris Saint-Germain’s season?

Few who witnessed this could bet against it: Unai Emery’s side blew Barcelona away with a scintillating performance that felt like a changing of the established order. Two wonderful finishes from Angel Di Maria, along with crisp drives from Julian Draxler and Edinson Cavani, sent Barcelona spiraling to a 4-0 defeat and, in truth, the damage could have been even greater. Assuming they see out the second leg, a huge psychological block might just have been removed from the French champions.

A pulsating atmosphere inside the Parc des Princes demanded a fast start from the home side, and it got one. Within four minutes, Marc-Andre ter Stegen raced well out of his goal to prevent Blaise Matuidi reaching an Di Maria pass, and moments later they carved Barcelona open again.

Cavani might have taken another Di Maria ball on his left foot but instead checked inside and allowed Sergi Roberto to block. It was relentless stuff from PSG, and in the 11th minute, Matuidi burst into the left side of the box only for Ter Stegen to save.

The question, at that early stage, was whether they could possibly keep this tempo up. It was answered six minutes later when Samuel Umtiti fouled Julian Draxler, who had turned him 2 yards outside the box. The position seemed perfect for Di Maria’s left foot and his subsequent shot, lifted over the wall past a motionless Ter Stegen, proved the impression correct.

Barcelona took 28 minutes to show anything of note, but their first genuine threat could have brought an equaliser, with Kevin Trapp saving well to deny Andre Gomes. But PSG continued to press and, five minutes from half-time, they had their second. This time it was Draxler, timing his run onto a wonderfully weighted Marco Verratti pass and cracking his finish across Ter Stegen before wheeling off in celebration.

Remarkably, it got even better. Ten minutes after the break, with PSG having picked up where they left off, Di Maria brought the ball forward to the right of centre with little challenge. He had time to pick his spot and did, finding the top corner superbly from 20 yards.

With Barcelona offering nothing in response, Cavani rounded off the scoring 19 minutes from time, finishing sharply after right-back Thomas Meunier had (not for the first time) rampaged forward.

It was that kind of night: PSG just didn’t stop, though their opponents had wilted long before the end.

2. Emery’s mercurial talents deliver in style

What a reward this was for Emery, who put his faith in two mercurial talents and saw them both deliver in sensational fashion.

In the post-Zlatan Ibrahimovic era, there has been an emphasis on the collective at PSG, and it was fair to wonder whether Di Maria and winter signing Draxler could both be accommodated in a tightly functioning unit. Yet on Tuesday night, they were irresistible; if they can repeat this kind of form, there’s little reason why the pair can’t drive PSG all the way to the final in Cardiff.

Di Maria has not always convinced fans in Ligue 1, but on the day he turned 29, he produced the kind of top-level performance they were crying out for. So tuned-in has his radar been during the early stages that, as he sized up that free-kick, it was hard to feel he could miss. He was irrepressible from the start, drifting inside from his starting spot on the right to dictate the game alongside the equally outstanding Verratti.

PSG’s movement, interchanging and invention from midfield were impossible for Barcelona to handle, and they could easily have been out of sight by the break. When Di Maria crowned his performance with another perfect finish, moments before being replaced by Lucas Moura, you sensed that they now were.

Draxler has had the air of a man with something to prove after his move from Wolfsburg, and, like Di Maria, he looked in the mood from the beginning. It was his willingness to roam across the pitch from his nominal position on the left that won the set-piece from which Di Maria started things off. His goal, superbly taken, came after the pair had switched sides and their ability to shapeshift confounded Barcelona repeatedly.

Like Di Maria, Draxler departed early, replaced in the 86th minute by Javier Pastore. His work was done and Emery’s faith had paid off in some style.

3. Dejected Barca have no answer

How do Barcelona come back from this? It’s hard to remember them being overrun in a European fixture to this extent, and it will take, even by their standards, something special at the Camp Nou to make a contest of the second leg. They simply could not cope with their opponents’ tempo, either on or off the ball, and they might count themselves fortunate to return home only four goals down.

The Spanish giants were forced into errors from the first few minutes, but the major surprise was the passivity that they offered in return. Their malaise was epitomised by the move for Draxler’s goal. Lionel Messi, already forced to track back to a degree hardly seen during his career, was dispossessed by Adrien Rabiot, and by the time the ball was worked to Verratti, Barcelona were in huge trouble.

When Sergio Busquets misplaced the simplest of midfield passes to a marauding Rabiot shortly before Di Maria’s second goal, you sensed the game was up. Yet the opportunity for a response in the second half had been there: instead, forced errors were joined by unforced ones and Luis Enrique’s side, whether comprehensively rattled or completely short of the stomach to fight this out, looked shot.

The ease with which Di Maria and Meunier were able to advance for the third and fourth goals, was remarkable, and you would have to stretch the mind back some way to find a time when Barcelona — even when not at their best with the ball — have given top-level opponents this kind of time and space to play.

Messi, who cut a dejected figure all night, was frustrated by the 21-year-old Champions League novice Presnel Kimpembe, and the standout moment of their battle came when the PSG defender thwarted him with a perfect tackle on the edge of the area just after the hour mark. He and his teammates would have had a slither of hope had Umtiti not headed against the post with seven minutes left, but Barcelona leave Paris having received precisely what they deserved.