Napoli s Nigerian forward Victor Osimhen celebrates towards the fans tribune after opening the scoring during the Italian Serie A between Napoli and Cagliari on September 26, 2021 at the Diego-Maradona stadium in Naples (AFP)
Luciano Spalletti's side cruised to their sixth victory in as many league games against a Cagliari team coached by former Napoli manager Walter Mazzarri thanks to Victor Osimhen's sixth goal in all competitions this month and Lorenzo Insigne's second-half penalty.
They are two points ahead of AC Milan after another confident display that ends a week in which they scored 10 goals without reply in three league matches.
Next weekend Napoli travel to Fiorentina in what will be the first true test of their title credentials, as their 2-1 win over Juventus earlier this month came against a team missing a host of starters.
They made easy work of a passive Cagliari, with Osimhen making it four Serie A goals in five appearances this campaign in the 11th minute when he met Piotr Zielinski's low cross with a typically assured finish.
Osimhen was involved again when a low-key match was settled in the 57th minute, the in-form Nigeria attacker being cleaned out by Diego Godin and Insigne lashing home the subsequent penalty to ensure a simple win.
Lazio win derby honours
Goals from Sergej Milinkovic-Savic, Pedro and Felipe Anderson gave Lazio a tight derby win over Roma at a raucous Stadio Olimpico which saw two teams attack each other for 90 minutes.
Maurizio Sarri's side were winless in three league matches heading into the weekend but now sit sixth on 11 points, seven behind Napoli and just one behind fourth-placed Roma, who twice pulled goals back through Roger Ibanez and Jordan Veretout.
"We needed a derby win to help us move forward and take on the coming matches," said Milinkovic-Savic.
"I like scoring in the derby, it's already the third time that I've done it and I hope to keep on doing it."
In the aftermath Mourinho lashed out at referee Marco Guida and the VAR officials after what he saw as a clear foul on Nicolo Zaniolo just before Lazio launched the counter-attack which ended with former Roma player Pedro putting Lazio 2-0 ahead in the 19th minute.
"The referee and VAR weren't up to the standards of a match of this level. From 2-0 it could have been 1-1, the referee made a mistake on the field and VAR made a mistake... they all made a mistake," Mourinho said to DAZN.
"My team was the better one... the second and third goals are counter-attacks and the second goal is also one in which the team was waiting for a penalty. We played, we tried, we dominated."
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)