Massimiliano Allegri could not hide his delight as Juventus tripped up Serie A leaders Napoli to deliver a psychological blow to their title challengers at their San Paolo Stadium.

In an key early clash in the battle for the Scudetto defending six-time champions Juventus move second just one point behind Napoli, who suffered their first defeat in 15 games this season.

Inter Milan -- now the only unbeaten team -- can claim the championship lead on Sunday when they host Chievo as Roma kept well within the title chase with a 3-1 win over 10-man SPAL on Friday to sit fourth, just four points behind Napoli with a game in hand.

"We needed a real Juventus performance tonight and that's what we produced," said Allegri after ex-Napoli man Gonzalo Higuain -- playing just days after surgery on a broken hand -- scored the only goal after 12 minutes.

"We had to dig in because we were up against a great side but we didn't give them an inch," continued the Juventus coach.

"Perhaps we've focused more on trying to play nice football than being solid up till now, but the big games are won in defence, and so we proved tonight."

Allegri insisted however that Napoli -- looking to end their 28-year wait for the Serie A title -- remain the team to beat.

"We may have won today but we're not the favourites for the title – Napoli and Inter are. 

"If we want to win a seventh straight title – after three years when we've fought to the end in pretty much every competition we've played in – we're going to have to produce something extraordinary. Ordinary is not enough."

- 'Phenomenon' -

Juventus skipper Gianluigi Buffon made some key saves for a clean sheet on the night, in a boost ahead of next week's Champions League trip to Olympiakos in Greece.

"It had been a while since I kept a clean sheet here – it feels good!" said former Italy keeper Buffon after his side's first win in Naples in nearly three years. 

"Our mentality and approach were spot on and we stayed tight as a unit. 

"If we play like that, we send out the message that Juve are in the mix and we're here to stay. Let's not get carried away just yet though: if Inter win on Sunday, we'll still be third, and I'm not going to celebrate third place."

Napoli coach Maurizio Sarri said the individual brilliance of Higuain, who left in 2016 for Turin in a 90 million-euro ($106 million) deal, was the key for the champions.

"Higuain is a phenomenon in these situations. Juventus have 90 million euro less in the bank, but an extra three points. I know Juventus are not loved in Naples, but while Gonzalo was with us, he behaved impeccably."

Napoli were also badly missing Polish striker Arkadiusz Milik whose knee ligament injury means Dries Mertens remains the only centre-forward.

"Unfortunately, Arek got hurt at the worst time, as the transfer window was closed and we couldn't bring anyone else in," saud Napoli captain Marek Hamsik."

Napoli take on Feyenoord in the Netherlands in Champions League next week looking to qualify for the last 16.