Break the transfer window and also the world cup will still have an effect on the team. Even though they are not part of the national team squad that represents their country for world cup. Example the physical and mental health of the players that will change when the league returns. This is something that the teams who are fighting for the championship need to be wary of. Changes in the formation of opposing players from the transfer window can make the opposing team better. So, Napoli must be careful and maintain the physical and mental players in order to continue to appear consistent after this break.
If we consider the resumption of the championship as a restart, then Napoli should not experience problems, since the first half of the championship is always successful for them. The problem is that it will be an "unusual" start of Serie A and different players will be in a completely different state after the break (those who rest will be retrained and those who play will be tired). Everyone will need an individual program to get back into Serie A games again. But I think Napoli's medical/therapeutic team can do it.
Napoli will not worry about this to start Serie A when the world cup is over, surely the players and coaches will have time to polish their players again to keep performing well in training sessions before the competition starts. Yes, there are indeed a number of teams that will be a little overwhelmed in dealing, especially if the players are injured in the world cup. however, Napoli this season has been quite consistent in every game so when the games start again I think they will be able to maintain their positive trend, but one thing that can make them lose control if several Napoli players choose to leave in January later, of course this is very detrimental to Napoli if they have to lose core players in january.