Juve are top on 51 points, three clear of the Nerazzurri, who also drew their previous two league games against Atalanta and Lecce 1-1. Lazio, who have a game in hand, inched onto 46 as they ended a run of 11 straight wins on Sunday.

Cagliari are sixth on 31 points in the Europa League zone, while Napoli are 10th on 27.

Napoli's Piotr Zielinski tapped in on 63 minutes after Wojciech Szczesny saved a taut Lorenzo Insigne drive to stir up a tactical and uneventful game at Naples' San Paolo.

Juve had no telling reaction and conceded again when Insigne struck with four minutes left, with a slight deflection from defender Matthijs de Ligt.

Cristiano Ronaldo pulled one back in the 90th, flicking in a long ball to be on target for an eighth successive league game.

At Milan's Giuseppe Meazza, Inter's Lautaro Martinez headed home in the 29th off a cross from Ashley Young, who made his debut after his arrival from Manchester United last week.

Cagliari captain Radja Nainggolan levelled against his former team with 12 minutes to go with a low, long-range drive.

Martinez was red carded in stoppage time for insulting the referee after being booked.

"I think we played well from the start and had good ball control," said Nainggolan.

"I think we played a great game and deserved to draw."

The Rome derby saw Roma produce a breathtaking start and go ahead when Edin Dzeko nodded home with the back of his head.

The Giallorossi, however, gifted Francesco Acerbi a 34th-minute equaliser as goalkeeper Pau Lopez fumbled a high ball.

Roma winger Lorenzo Pellegrini hit the post and after the break saw his captain Dzeko fire at keeper Thomas Strakosha.

Roma went fourth past Atalanta on 39 points to fill the last available Champions League place.

Elsewhere, seventh-placed Parma won 2-0 against Udinese, promoted Verona went ninth after beating Lecce 3-0 and Sampdoria drew 0-0 with 10-man Sassuolo.

Saturday action saw Atalanta hammer Torino 7-0 away as Bologna beat SPAL 3-1 and Fiorentina drew 0-0 with Genoa. AC Milan edged Brescia 1-0 as they opened matchday 21 on Friday.

Australian Associated Press