What Chelsea did to PSG in the FIFA Club World Cup is definitely demoralizing but I'm sure that Luis Enrique would have taken the lesson learnt to correct that fatigue that befell them. Instead of hindering them next season Champions League, it will even motivate them more and make them not to underestimate any team. Even in the French Lig 1, PSG is still the favorite to win it with little resistance from any team that might peak up for next season.
You know FIFA Club World Cup is not a very important title. Actually I don't think Les Parigos are too sad because they lost. Also fans are happy because they managed to beat giant clubs like Real Madrid and Munich. This is one of Luis Enrique's biggest achievements this season. They should learn from this defeat. They conceded 3 goals but failed to score a single one. Luis Enrique has to find out what is the reason for the Red and Blues sudden decline. If Luis Enrique is able to identify the weaknesses of the squad, then I believe they will come back stronger next season. The players have this ability, also has an experienced coach like Luis Enrique.