Edinson Cavani scored a hat-trick in a 3-1 win over Inter Milan to take his goal tally to 101 in a Napoli shirt and reinforce second place in Italy's Serie A on Sunday.
Juventus earlier secured their 29th title with a 1-0 win over Palermo which guaranteed the Turin giants a place in next season's Champions League for the second consecutive season.
Napoli, meanwhile, appear about to follow in the champions' footsteps after a 21st win of the season which restored their seven-point lead over AC Milan, who are third with three games remaining.
Napoli now need three points to cement the runners-up spot, but coach Walter Mazzarri said: "We're not taking anything for granted.
"There are still three points to pick up."
Mazzarri admitted Juve had simply been superior this season.
"We've garnered 17 more points than last season, which speaks for itself.
"But we were up against a Juve side that was out of this world.
Despite Mario Balotelli scoring a late winner to hand Milan a precious 1-0 win over Torino earlier on Sunday, Napoli settled quickly into their game against an Inter side which has been decimated by injury.
Cavani started the game with a league-leading 23 goals but had seen Antonio Di Natale of Udinese move on to 20 with a double in a 3-1 win over Sampdoria.
But the Uruguayan gave Napoli a dream start with a third-minute lead when he beat Inter 'keeper Samir Handanovic after a long ball from Goran Pandev caught out the visitors' defence.
Inter levelled 20 minutes later when Ricardo Alvarez beat Morgan De Sanctis in the Napoli net after he had been fouled in the area by Juan Zuniga.
Cavani was offered the chance to score his 100th goal for Mazzarri's side when Jonathan clumsily fouled Zuniga in the box, and the Uruguayan did not disappoint the full capacity San Paolo stadium when he beat Handanovic in the bottom corner.
Inter had failed to beat Napoli away since 1997 and that statistic grew to five defeats and two draws in that period when Cavani sneaked in at the back post to send Pandev's cross high into the net in the dying minutes.
Cavani's exploits this season have earned interest from Paris Saint Germain, Manchester City and Real Madrid who are all reportedly set to finance a buy-out clause of 63m euros to land the Uruguayan.
When asked of the rumours, Cavani would only tell Sky Italia: "I am just concentrating on doing my best, then we'll see.
"I am not thinking about the future, only Wednesday's game against Bologna that can directly qualify us for the Champions League."