Mazzarri didn't make Napoli's performance improve, in fact it made Napoli's performance worse every week, when facing Genoa on the last matchday, Napoli was only able to score 1 goal in the 90' minute, Kvarat didn't even have a chance at all, from this i understand that figure A coach is very important for a team, when the coach doesn't provide a good strategy, the squad being coached will play chaotically. Napoli's position in the current standings is increasingly in the middle, facing Cagliari later, they must win, in order to improve their position in the standings.
You are right that statistically Napoli performance under Mazzarri coaching has not improved, so it is very natural for the Napoli owner to fire him. Napoli is still stuck in the middle of the standings because Napoli is ranked 9th in the standings. In tomorrow's match, Napoli will be led by their new coach, where Calzona is expected to bring victory to Napoli when they visit Cagliari headquarters. In terms of opponents, of course they are quite weak because until the season enters the 26th match, Cagliari is still in the relegation zone.
So, Cagliari imbalance in performance must be able to be exploited by Napoli in tomorrow match. Calzona must be able to awaken the strength of Napoli players like Osimhen and Kvaratskhelia because if these two players find their best quality form then Napoli can easily win in tomorrow match. Apart from that, Cagliari will also try to find a win at home and for that reason their chances in tomorrow match are certainly big, but on condition that they have to play better to be able to beat Napoli.