1. Intensity in pressing opposition
Right from the opening it was clear the difference in intensity when it came to pressing.
Barca have struggled this season when pressed very high. Close down Ter Stegen and cut-off his passing options you'll put Barca under serious pressure. PSG did this from the first minute.
Luis Enrique's side on the other hand...
Right from the start we can see how PSG will make life very difficult for Barca, knowing that by pressing them high up the pitch they are unable to build up the play and therefore leave Lionel Messi, Luis Suarez and Neymar isolated up front.
We can also see that Barca, who over the years have been so successful in the way they press the opposition, do position themselves high up the pitch but put little pressure on the ball, fail to cut-off passing lanes and let PSG's midfielders run free in the middle of the pitch.
It may sound simplistic, partly because it is, but against the best you need to cover a lot of ground. That doesn't mean run around for the sake of it, but PSG coach Unai Emery has trained his side when and where to make the right runs.
PSG as a whole ran 8,176 meters more than Barca. Given the average Barca player ran 9,555 meters, that is almost like having a 12th player on the pitch.
In just the third minute PSG showed how they could threaten Barca on the counter-attack with pure speed.
Within four minutes PSG have managed to do two things Barca hate, press high and counter with speed.
2. Targeting Barca's right side
Barca have had problems in this area of the pitch ever since Dani Alves left at the end of last season. Sergi Roberto has done admirably in this position given he's a central midfielder but he is still considered a weak point for opposition sides. Meanwhile Andre Gomes has yet to impress in his role as a right-sided central midfielder, both in attack or defence.
In order to compensate, Barca often send reinforcements in the form of central-midfielder Gerard Pique or defensive midfielder Sergio Busquets.
Di Maria's second goal and PSG's third, exposed why this can be a big problem, as it opens up space in the middle of the pitch to exploit.
As Busquets moves across to help Gomes and Roberto he leaves space for left-back Kurzawa to come inside which leads to a wonderful goal from Di Maria.
3. Switching strategies after taking the lead
Early in the match PSG pressed high as shown above, but after taking the lead they got numbers behind the ball, allowed Barca to have the ball in wide areas while blocking the centre of the pitch. As soon as they won the ball they looked to hit Barca behind their full-backs.
Emery knew that Barca would push forward regardless and that would leave spaces on the counter attack.
Often when Barca struggle to build up from the back Messi, whether out of frustration or necessity, drops into deep midfield.
This turned out to be a big mistake, as Rabiot excellently robbed Messi of possession, then Verratti was able to set up Julian Draxler who made the most of the space left by Jordi Alba to make it 2-0.
4. Individual brilliance of Di Maria and Rabiot
While Unai Emery is deservedly getting praise for his strategy and game management, the performances of Angel Di Maria and 21-year-old Adrien Rabiot were sublime.
Di Maria scored two beautiful goals and created numerous chances for his teammates. Meanwhile Rabiot was exceptional in a deep midfield role, he completed the most passes (55) for PSG and gained possession an incredible 12 times.
He even managed an outrageous nutmeg on Messi!
Enrique's days are numbered
Luis Enrique has been under pressure for sometime, the individual brilliance of Messi, Iniesta, Suarez and Neymar often over-shadowing the disjointed performances of the team as a whole.
Barring a miracle, he will be gone at the end of the season. Almost certainly out of the Champions League at the Round of 16 - their worst result since 2007 - potentially seven points behind Real Madrid when they play their two matches in hand in the league. It is unacceptable for a club as big as Barcelona.
The local media, unforgiving at the best of times, smell blood. Reports of players dissatisfied with the manager are already being leaked from the dressing room.
Barca were lethargic in closing PSG down. There build up from the back was insipid. The result was bad, the performance worse. Today's match marked the end of a roller-coaster time at the helm of one of the world's biggest clubs.