In only 14 matches this season, he has scored 11 goals and dished out nine assists. This is a very positive record for him so far.
I am sure that Lionel Messi and Mbappé are going to be able to play well for PSG. I am not sure if Messi will be able to perform as well without Neymar, and this is my main concern at this point. Because we all know that Messi is a great friend of Neymar, but he does not have that type of friendship with Mbappé at all. So, I personally think that if Mama takes a long time to recover, it is going to be a problem for PSG. Especially in Champions League matches.
Right now both Argentina and France having fair chance for the title in World Cup with this most chances these both players will be played for some more time, and hopefully they will end this cup without any serious issue because nothing's could be tricky as full strength needed for all countries as we are entering into last 16 round and Neymar injury is surely big setback for the Brazil which is also favourite for the title.
Maybe the worst case would be him missing rest of the world cup, and not play in a few easy games at first, then 20-30 minutes in other games and then he could play 70+ minutes for PSG when they need him in the UCL, that would be the worst case, and even that's not bad. Better case would be him being ready by quarter or semi finals during world cup, and he would be fully ready when he goes back to PSG.
Now there are two things that can be done. Even playing for Brazil four as much as he can whenever he gets a little bit healthier. Just so that he can play in the World Cup. Which is obviously going to have a devastating effect on his career. And the other thing is going to be waiting to get healthy so that he can play well for PSG in the Champions League. I think he should be wise and choose the letter option.