The superstar duo missed PSG's trip to Germany to take on RB Leipzig in the Champions League during the week, with them eventually losing 2-1 despite going 1-0 up and missing a penalty in the first half.
There was a noticeable, natural drop in quality in the PSG frontline without Neymar and Mbappe, but head coach Thomas Tuchel will have to find a solution again, this time for Rennes.
Unfortunately for the German, he simply does not have the raft of options to make too many changes from the loss against RB Leipzig.
With Mauro Icardi still injured, Moise Kean will be trusted with a starting berth up front again, while Pablo Sarabia and Angel Di Maria will support from the flanks.
Leandro Paredes is reportedly back in contention, and he could be thrown straight back in here as the midfield of Marquinhos, Ander Herrera, and Idrissa Gueye was desperately lacking in creativity in the Champions League.
Should he come in, it could be at the expense of Presnel Kimpembe, who let his team-mates down with a ridiculous dismissal against RB Leipzig, scything down an opponent purposefully when already on a yellow.
Abdou Diallo could be recalled, too, with Danilo dropping to the bench.
Marco Verratti and Julian Draxler are still out.