The Ligue 1 giants have swept all before them on the domestic front this season, but it has been a different story in Europe with only one win from their four Group C games so far.
Only one point separates the top three in the standings heading into matchday five, and wins for both Liverpool and Napoli would see PSG unable to finish in the top two and therefore consigned to Europa League football at best in the New Year.
Here, Sports Mole looks at how Thomas Tuchel could set his side out for the crucial contest.
The fitness of Kylian Mbappe and Neymar has dominated the buildup to this fixture, with PSG's star duo both picking up injuries during the international break which subsequently ruled them out of the weekend win over Toulouse.
Both players took part in training on Tuesday and are expected to start the game, though, restoring PSG's front three to full strength alongside Edinson Cavani.
There was more good news on the injury front at the weekend as Dani Alves made his first appearance of the season off the bench, while Layvin Kurzawa was also included in the matchday squad for the first time.
Wednesday's match is likely to come too soon for either to start, but they are available and will provide attacking wing-back options in Tuchel's new favoured 3-4-3 system.
Angel Di Maria could be forced to play as a left wing-back if Tuchel opts to partner Adrien Rabiot with Marco Verratti in the middle, but he may also be tempted to go with a more attacking lineup considering PSG's need for a win.
Gianluigi Buffon and Alphonse Areola have been swapping the gloves so far this season, but it was Buffon who started in the last Champions League game and at the weekend, so he appears most likely to get the nod on Wednesday.