I am hardly surprised at the defeat of PSG,they have an important match against Real Madrid in Bernabeu stadium and their full focus is there.They sure play the games in the Ligue 1 but their concentration is normally not being the same as the one they will have in the return leg against Real Madrid.
It is not acceptable result for PSG they have. But they can not blame on Champions League because PSG have good players for their second squad so that they can win many matches in Ligue 1 with their second Tier players. Sometimes their substitute players can not perform well after long time on the bench but it is not all to assess their quality
Also the fact that Neimar missed the penalty does not surprise me,they are already 13 points ahead and they are already Champions of the Ligue 1 this season,other lost games can be expected from PSG and they are not a safe team to bet on the Ligue 1 anymore at least for this season.In Champions is a completely different story as that is now their main objective.
Neymar has never been in his best in this season. Over weighted, got injuries, lot of time to recover, unhealthy habit and he is going to his 30. It is bad to see Neymar is going towards downside of his career without good recognition as ther third best players under only Messi and Ronaldo.
This season, Messi and Ronaldo don't have good performance and I belelive important reason is their ages. They have more professional than others and with their talent, they become legends. Neymar has taldnf but unprofessional and his bad habit restrict him to join top players