Rarely has a coach’s job depended on the Italian Super Cup, but rarely has Juventus got off to a worse start to the season over the past decade.

The match showcasing the Serie A and Italian Cup champions is normally regarded as little more than a friendly. It used to be the traditional season curtain-raiser in August but has been played in December or January several times over the past few seasons.

Anything but a convincing win for Andrea Pirlo’s Juventus over Napoli could spell the beginning of the end of his brief time in charge. Eyebrows were raised when the 41-year-old Pirlo was given the reins at Juventus at the start of August, handing the former midfield maestro his first-ever coaching job. And for now, the doubters are being proved right.

Pirlo was tasked with turning Juventus into a more attractive side and ending the club’s quarter-century wait for Champions League success. The Bianconeri were not expected to falter in Serie A, which they have dominated for the past nine seasons. Juventus lost 2-0 at bitter rival Inter Milan on Sunday to leave it fifth, seven points below the Milan sides, which lead the standings.

The Juventus swagger, created by winning nine successive Serie A titles and being the team to beat in Italy for so long, is gone and in its place is doubt and even fear.

"When you go out onto the field anxious and scared everything becomes more difficult," Pirlo said. "We couldn’t have put in a worse performance than this but now we need to pick ourselves up because we’ve got a cup final on Wednesday." The loss was only Juve’s second in the league this season but comes less than a month after a dreadful 3-0 reverse at home to Fiorentina.

Moreover, Juventus is drawing matches it would have previously won and is nine points worse off than it was after 17 matches last season under Maurizio Sarri. The pressure to succeed at Juve is intense. Sarri was heavily criticized in his one season – and he won the league title. Such is the problem that even the players seem resigned. Cristiano Ronaldo was a shadow of his usual self at San Siro on Sunday and could only let out a rueful smile when Inter scored its second goal.

Juventus captain Giorgio Chiellini admitted that the Bianconeri’s domination of Italian soccer could be coming to an end.

"Time passes for everyone. Cycles sometimes end, we are trying in every possible way to ensure it continues," Chiellini said Sunday night. "Succeeding in winning a 10th successive league title would be something incredible: it won’t be easy but we are trying in every possible way. "We’ve got a cup final to play in three days, so we need to recover – we can't let this result floor us."

Juventus has won the Super Cup a record eight times. It lost to Napoli in the 2014 edition. Gennaro Gattuso's Napoli head into the match in Reggio Emilia in a very different mood, having thumped Fiorentina 6-0 on Sunday.