Injuries to key players could very well result in the team being inconsistent in winning matches so that teams like Nice and Monaco are often easily left behind by PSG, who are still kings in Ligue1. But if this is caused by player fatigue, I think we need to look at the playing schedule of the two teams this season in whatever league they are in. Because if both of them only play in Ligue1, I don't think their players will get tired easily because other teams' players do too, including teams that have high consistency in Ligue1.
Nice and Monaco who are very much in the race to the top of the table rightly behind PSG seem to be participating in a few tournament asides the Ligue 1 this season and PSG aswell is also a participant in the champions league asides the Ligue 1 but currently they don't have any champions league fixtures till February.
There's currently no known recorded case of injury with the PSG side and until their UCL fixtures they seem to have a very free schedule so I'm not expecting a case of fatigue with them until they begin to simultaneously participate in both leagues and same applies to Monaco and Nice, until then they may not have the privilege to take advantage of fatigue on PSG to get to the top of the table but I'm very optimistic about PSG strategy on fatigue management such that it's not going to be so much of a problem that it will take them off their spot on the table, they are most definitely still going to survive their position on the table and most likely win the trophy this season.