Yes, that's what I'm worried about and sometimes even a new coach will have difficulty providing direction in a team whose quality is very even. We know that Napoli's squad is filled with good players, especially Osimhen and Kvaratskhelia, so if Mazzarri cannot provide his strategy to these two attacking players then he is definitely a failed coach. Sometimes it is not an easy problem to solve being at a club with an even squad depth and if the desired results are not comparable then he will be under more pressure. Responsibilities as a coach at a club with the status of defending champion will certainly become more mentally distracting. However, it looks like we will first see his journey in leading Napoli and if the results continue to be positive then he can get full attention and support from the squad and fans.
There are rumors that Napoli wants Conte but may not be able to get the services of the coach and ultimately return for Mazzarri who I don't think will be too difficult with the current Napoli squad.
Mazzarri can show his quality until his contract runs out. This is a short contract I think Napoli also has other coaches in mind for next season. If it's impossible for Mazzarri to perform well, he could get a longer contract, not just to finish this season.
Napoli should go for some other coach. Someone who is definitely going to be better and someone who has proved himself in the past. I understand that they are always looking for Italian coaches most of the time. But I don’t think that is going to work very well. at least right now when there is a shortage of good coaches.
I do not think that extending the cult contract is going to help them too much. In my opinion, the coach is not going to be able to bring in incredible results. So it will be better if they look for other coaches.