Defenders: Nuno Mendes, Sergio Ramos, Danilo, Pembele
You already know what's poppin'. In a matter of days PSG have lost Kimpembe, Marquinhos, Mukiele, and Hakimi to different lengths and are now looking at a defensive unit that basically comprises two left-backs, two center-backs, a makeshift CB, and a right-back. And some of those players aren't even remotely close to the levels you might expect from someone donning the PSG threads.
With only "three" center-backs healthy, if you consider Danilo one although his natural role is that of a defensive midfielder, the most logical thing would be to ditch the three-CB line in favor of a two-man backline flanked by two full-backs. That would at least prevent PSG from suffering a true catastrophe in the event of an injury happening to Danilo, Sergio Ramos, and/or El Chadaille Bitshiabu.
If Galtier wants to go with the "strongest" team, as he often says, then the best defense he can field today would feature Nuno Mendes on the left, Ramos and Danilo in the center of the line, and Timothee Pembele on the right if only because there are no more warm bodies available. You be the judge whether thats a "strong" defensive unit or not.