After the world cup, there may be differences in appearance for some of the top teams in Serie A, especially for teams whose players are used in world cup matches. Of course they will be very overwhelmed and tired, even potentially injured. But in general Napoli will still try to perform well after the world cup because not many of their players have been involved or called up by the national team in this world cup.
World Cup have two impact side for team, positive side with their player have on the high physical quality because one months keep in training center with their national team, but have negative impact for team when their player return back later with injured. I think have different appearance with top team standing in Serie A later based on how many main player get injured after World Cup. Lately have one player confirmed with injury is Neymar, just waiting few matches later who become next player get injured and give bad thing for their current team.
Napoli in the top standing right now need controlling their player without any serious injured when returning back to the team, I think if not any player injured nothing difference standing position in Serie A and Napoli can continues consistency performance.