How to watch Barcelona PSG
Messi and Barcelona face PSG in the Champions League on Tuesday. Eitenne Laurent/EPA.

It was one of the most memorable nights in Champions League history and, in hindsight, the moment Barcelona and Paris Saint-Germain’s fates started to become intertwined. We still talk about the Catalans’ astonishing comeback from a 4-0 last-16 deficit to the French champions to this very day. The knock-on effect from that game, however, has been just as compelling to track.

The story goes that Neymar made his decision to leave Barca that night. The Brazilian felt he’d played one of the games of his career, scoring twice and providing the assist for Sergi Roberto’s all-important stoppage time winner, but found himself in Lionel Messi’s shadow, whose image plastered the front pages of the newspapers the following morning.

While no contact between Neymar and PSG was made until closer to the summer, the first vines of fate had started to bind Barcelona and the Ligue 1 outfit. Now, the two clubs will meet again in the last 16 of the Champions League in what could prove to be a season-defining encounter for all involved.

Barca find themselves in the midst of a transition both on and off the pitch. Financial and political turmoil have engulfed the Camp Nou over the last 12 months, with the club treading water until the election of a new president after Josep Bartomeu was forced out. Ronald Koeman’s side are currently eight points off the top of La Liga in third place — far from their peak years not long ago, when they ruled the Spanish game.

Having made their first Champions League final appearance last season, PSG sacked manager Thomas Tuchel and replaced him with Mauricio Pochettino. The former Tottenham Hotspur boss has made a good start to life in the French capital, but his fingerprints are still very light on a group of players he has had very little time to work with.

Nonetheless, Pochettino will be defined by what he can achieve in continental competition. ‘Project PSG’ has always been about delivering the most prestigious prize in club football to the Parc des Princes. Defeat to Barcelona won’t be tolerated despite all the mitigating factors. This is an early litmus test for the new man in the job.

Pochettino has made some changes in terms of personnel, with Mauro Icardi restored to the starting lineup and Marquinhos moved back into central defence to fill the void left by Thiago Silva at the end of last season, but PSG are still largely the same team tactically that they were under Tuchel.

Of course, the underlying storyline to this match concerns the future of Lionel Messi. The 33-year-old is out of contract as a Barcelona player at the end of the season and PSG are believed to be preparing a sales pitch. Public remarks have been made by sporting director Leonardo and even Angel di Maria, who was very open in expressing his hope that Messi will join PSG in the summer.

“It's wrong to say such things, especially because it heats up our Champions League match even more,” Koeman hit back at di Maria following his remarks. “I think it's not fair and it's disrespectful to talk so much about one player who is still playing for Barcelona.”

Two summers ago it was Barcelona who were guilty of speaking about a PSG player, Neymar, in the media, with the Brazilian coming close to securing a return to Catalonia. Seemingly regretful at having left the Camp Nou, Neymar desired a reunion with Messi. He might still get his wish with Messi the one making the transfer.

Even by usual standards, there is a lot on the line for these two clubs. Whichever team wins will be emboldened as they move into the Champions League quarter finals. Whichever team loses will face relentless questioning, and defeat will be taken as a sign of failure. Pochettino would likely survive and be given a second chance to prove himself. Koeman might not be so lucky.

In many ways, it feels as if these two clubs envy each other. Barcelona surely look at the resources available to PSG with jealousy, such is the perilous financial situation the Catalans are in right now. PSG, on the other hand, almost certainly covet the sort of credibility Barcelona enjoy in the sport.

There is a lot that links these two clubs, down to the colours of their kits, but Tuesday’s Champions League encounter will once again see what divides them come to the fore – and surely change each club's respective trajectory.