Maurizio Sarri targeted by fans as Cristiano Ronaldo goal can't save Juventus on return to Napoli

Juve miss the chance to open six-point lead after 2-1 defeat against coach's former club

Juventus forward Cristiano Ronaldo receives a yellow card from Italian referee Maurizio Mariani against Napoli. AFP

Napoli's Piotr Zielinski celebrates after putting his side ahead. EPA

Lorenzo Insigne celebrates the second goal. AP

Cristiano Ronaldo pulls a goal back for Juventus. EPA

Lorenzo Insigne celebrates with teammates at the end of the game. AP

Napoli players celebrate after their victory over Juventus. AP

Juventus coach Maurizio Sarri with Napoli coach Gennaro Gattuso before the match. Reuters

Struggling Napoli shocked champions Juventus to spoil coach Maurizio Sarri's return to the Stadio San Paolo.

Sarri had not been back to Naples since being sacked in May 2018 after three successful campaigns, and before moving to Chelsea.

This season he has taken over eight-time reigning champions Juve, a move seen as a betrayal by his former team, the two-time Serie A runners-up.

Juve missed the chance to open a six-point lead on Inter Milan at the top of the table after a 2-1 defeat.

Clear opportunities were few and far between, and Juventus didn’t have a shot on target in the first half for the first time this season.

"It is pleasant and exciting to go back," said Sarri despite the whistles and insulting banners of his former fans, reserving his criticism for his "under-par, mentally bland" team.

"We lost a match against an opponent who had done the minimum to win," he added.

"We were passive throughout the game, always halfway between pressure and waiting, we made mistakes."

Piotr Zielinski broke the deadlock after 63 minutes finishing off a rebound after Lorenzo Insigne was denied by Juve goalkeeper Wojciech Szczesny.

Insigne volleyed in a second after 86 minutes to an explosion of joy among the crowd.

Cristiano Ronaldo pulled a goal back as the game headed into injury time for his 13th goal in nine consecutive games in all competitions.

Napoli move up to tenth place, 12 points off the Champions League places, after ending a run of three consecutive defeats.

"It's a victory for the whole of Naples," said Insigne after his team's first home win in the league since October 19.