Piotr Zielinski and Lorenzo Insigne scored in the second half as struggling Napoli shocked champions Juventus 2-1 to spoil coach Maurizio Sarri’s return to the Stadio San Paolo on Sunday.

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 up a six-point lead on Inter Milan at the top of the table, after Antonio Conte’s side were earlier held 1-1 by Cagliari, their third consecutive draw.

Inter are three points behind Juve with Lazio a further two points adrift in third after city rivals Roma ended Simone Inzaghi’s side’s 11-match winning streak.

“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.

 In Naples, Zielinski broke the deadlock after 63 minutes finishing off a rebound after 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.

The visitors pushed for the equaliser but Alex Meret smothered Gonzalo Higuain’s goal-bound effort, as Juve crashed to just their second defeat of the season.

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

In the San Siro, Radja Nainggolan claimed the equaliser for Cagliari against his parent club Inter.

Tensions reached boiling point as Inter’s goalscorer Lautaro Martinez was sent off in injury time for arguing with the referee.

The Argentinian reacted with fury, shouting and repeatedly punching the plexiglass at the side of the pitch, as he was led away by his teammates.

Martinez’s frustration mirrored that of his team, who have now been held to three consecutive 1-1 draws and taken 11 points from their last seven league games.

Inter made a promising start with Ashley Young having an immediate impact on his debut after arriving from Manchester United, providing the cross which allowed Martinez to head in after half an hour.

But the hosts failed to build on the momentum and the Sardinians stayed in the match until Nainggolan’s deflected long-range equaliser on 78 minutes.

Agence France-Presse