Midfielders: Marco Verratti, Fabian Ruiz, Vitinha
The strongest line of the team these days as the defense is boasting multiple wounded bodies and the offense is a one-man unit (Mbappe) with the other one (Messi) not giving a damn about one single thing anymore.
The trio of starters here should be the strongest possible one to hold the team together and make things work a bit for PSG while playing from the back and up the pitch. One would expect Marco Verratti to be perfect for that, but he's struggled mightily of late to find a proper form and level of play, so we'll see how that goes. Nobody is replacing him, though and reasonably, so expect him to get the starting call.
The other two positions are a little bit more up for grabs with Renato Sanches back and fit to play (I expect him to get some 20+ minutes on Sunday for the first time in ages) and Warren Zaire-Emery looking better by the day. Of course, Vitinha rested last weekend so it might make sense to rotate a bit (even though PSG are only playing for the Ligue 1 now...) and field him on the starting XI next to Verratti, as he seems to be the man with whome he plays best.
Fabian Ruiz usually has a great for every three bad outings, and all of those come out randomly, so you never know what to expect from the Spain international. He is the best and most established/veteran player available for Galtier, so I guess it's reasonable to expect him to start above WZE.
An interesting little golden nugget of information coming off Friday's training session is that WZE seemingly played makeshift-CB in a training match. That adds to the possibility of the young lad staying on the bench as an emergency reserve in the event of a defender suffering an injury.