Monaco's 2-1 win away at Guingamp has given Les Monegasques a three-point lead over second-placed Nice and a provisional six-point advantage over third-placed Paris Saint-Germain ahead of Le Classique on Sunday.
The men from the principality bounced back from their 5-3 UEFA Champions League last 16 first-leg defeat away at Manchester City with a narrow victory at Stade de Roudourou and now the pressure is on Unai Emery's men to get a result in Marseille.
If that was not pressure enough, the French champions are also travelling to Stade Velodrome without away supporters and will face a cauldron of noise when they step out onto the pitch at the home of their bitter rivals.
Although PSG defender Marquinhos insisted pre-match that a negative result against Rudi Garcia's side would not be "the end of the world" as far as Les Parisiens' title hopes are concerned, the reality is that it might actually spell the end of this season's duel with Monaco.
Should Marseille win this weekend, six points will surely be too big a gap to bridge between now and the end of the campaign. A draw would mean a five-point deficit and even overhauling that would be considered unlikely.
The only option for Emery and his players is to emerge from the Velodrome with all three points and keep Leonardo Jardim's prolific Ligue 1 leaders within three points. Even that, considering some of Monaco's remaining fixtures, might be enough to see the principality outfit home.
It will not be the Marseille result that really costs PSG if they fail to beat OM, it will be the two points dropped at home to Toulouse last Sunday that they are made to really rue. The pre-match gap should be three points and not six and that would have alleviated some of the pressure on this already high pressure fixture.
Instead, the current titleholders find themselves with their backs against the wall and heading into hostile territory at a pivotal moment in the term.
"Having faced Barcelona before going to Marseille gives you more confidence," right-back Thomas Meunier told PSG's official website ahead of the showdown clash. "We are going to find ourselves in a red-hot atmosphere.
"It is the kind of match in which millions of people have their eyes on you. So there is just one thing to do -- work well on the pitch.
"I am really excited about experiencing my first Classique at the Velodrome. It is for the atmosphere at these games that you play football. It is true there will be quite a lot of pressure but that is part of sport and you have to live with that. I am really looking forward to it!"
Emery will be without experienced midfielder Thiago Motta, who failed to prove his fitness in time to earn a place in the 19-man squad, so it is curious that the Spaniard has also omitted seasoned left-back Maxwell for no apparent fitness-related reason.
Grzegorz Krychowiak and Giovani Lo Celso are also absent but neither will be missed too sorely as they have not featured much at all lately.
Motta's unavailability gives Emery the chance to align a midfield three of Adrien Rabiot, Marco Verratti and Blaise Matuidi once again and if that trio can replicate their Barcelona form, then perhaps PSG can seize control early on at Stade Velodrome.
However, if returning captain Thiago Silva and Angel Di Maria are both rusty after their recent injuries and do not hit the ground running, the men from the capital could find themselves in early trouble.
Le Classique is always viewed as a must-win match for both sides but this time, it really is an absolute must for PSG. If they lose further ground on Monaco here, there is a very real chance they will be unable to claw it back again.