It had been a bonkers, record-setting, night – one of the highest-scoring matches ever in a rivalry that goes back 115 years – but not all the protagonists were enjoying themselves. “Thanks for the show!” said Zvonimir Boban in the Sky Sport studio to Simone Inzaghi at full-time. The Inter manager winced and forced a laugh. “The neutrals like you enjoyed yourselves. Me, a little bit less.”

Inzaghi had seen his team fritter away a two-goal lead in the final 20 minutes against Juventus, letting 4-2 become 4-4. To write it that way does a disservice to Kenan Yildiz, the teenager who came off the bench to score twice and turn the game on its head – writing his name into Derby d’Italia lore. Yet to tell it any other way would ignore the truth that Inter could have been out of sight before he did.

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This was not the football we anticipated. Juventus are still a team in construction under Thiago Motta, hired this summer after steering Bologna into the Champions League. The Bianconeri had shown us different faces so far: adventurous and creative in some games but muddled and passive in others. They scored three goals in five of their first eight matches under the new manager. The others were all 0-0 draws.

They arrived here from easily their worst performance so far – a home defeat to Stuttgart in the Champions League in which they had one attempt on goal to their opponents’ 10. Still, the impression was of a team that, even on bad days, could at least keep it tight at the back. They had conceded once in eight Serie A fixtures.

Inter made a mockery of that statistic, scoring three before the interval. Juventus helped them out, giving away a pair of penalty kicks. The first arrived at 0-0, Danilo swinging at a cross but kicking Marcus Thuram instead. Piotr Zielinski, making his first league start since a summer move from Napoli, converted the spot-kick.

That was the 15th minute. Juventus were 2-1 up by the 26th. Dusan Vlahovic side-footed in the equaliser after Weston McKennie served him a delicious lay-off from a Juan Cabal chip over the Inter defence. The 21-year-old winger Francisco Conceição feather-footed his way past two Inter defenders to set up McKennie’s USA teammate Tim Weah.

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Inter responded with maybe the best strike of the night, Henrikh Mkhitaryan executing a one-two with Marcus Thuram on the edge of the Juventus box before threading a finish between three defenders and into the bottom corner of Michele Di Gregorio’s net. It was the first goal any Serie A player had scored against Motta’s side in open play.

From the sublime, we arrived at the ridiculous: Pierre Kalulu kicking Denzel Dumfries inside the Juventus box a fraction of a second before the Inter player was about to commit a handball. Zielinski’s penalty was perfection. For the first time in more than a century of competing, these teams had combined for five first-half goals.

When Dumfries made it 4-2 to Inter after the break, forcing the ball in at a corner, the game only seemed to be heading in one direction. He had missed another chance to score moments earlier. Di Gregorio made sharp stops to deny Federico Di Marco and Nicolò Barella soon after.

Enter Yildiz. A graduate of Juventus’s NextGen team, and prior to that Bayern Munich’s academy, the 19-year-old had already made 27 league appearances for the first team under Massimiliano Allegri last season – mostly off the bench – but has been taking on a more prominent role this year after impressing for Turkey at the Euros.

Despite playing the third-most minutes of any Juventus player, his performances had been a mixed bag. Yildiz made assists in each of his first two games this season, and scored a spectacular goal against PSV on his Champions League debut, but had struggled to make an impact since. National media carried interviews with former pros calling him “predictable” and wondering whether the No 10 shirt was weighing too heavy.

Udinese 2-0 Cagliari, Torino 1-0 Como, Napoli 1-0 Lecce, Atalanta 6-1 Verona, Parma 1-1 Empoli, Lazio 3-0 Genoa, Monza 2-2 Venezia, Inter 4-4 Juventus, Fiorentina 5-1 Roma

Yildiz sought to dispel all that in an interview with La Gazzetta dello Sport last week, describing himself as a “well-centred and balanced person”. There were hints of a normal teenage vulnerability as he acknowledged in the same breath that “I’m not happy spending time on my own”.

He has made a bond with Alessandro Del Piero, one of Juve’s all-time great No 10s, who sent him a towel to congratulate him on his first Juventus goal last year and has stayed in touch ever since. When the interviewer pointed out that Del Piero first made his iconic tongue-out goal celebration after scoring at San Siro, Yildiz replied: “I didn’t know that. I’ll have to try to replicate it.”

Detto fatto, as they say in Italy. Said, and done. Yildiz kept his tongue in his mouth after he cut the deficit to 4-3 in the 71st minute, perhaps as surprised as everyone else by Dumfries backing off to give him the space to run into the Inter penalty box and drill a shot across Yann Sommer. But it came out after he scored again to equalise at 4-4.

Sommer was slow to react on both goals, this time letting the ball squirm underneath him when Yildiz fired the ball in from a half-cleared Conceição cross. With Fiorentina thrashing Roma 5-1 in Sunday evening’s later game, this was a bad night for tired cliches about Italian teams being hard to score against.

It was a very good night for Antonio Conte. After winning the Derby d’Italia as manager of Juventus, and then as manager of Inter, he had somehow now won it as manager of Napoli – this result allowing his team to finish the round with a four-point lead at the top of the division.

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It is still early to worry about such things, and the next six weeks might be the toughest stretch – on paper, at least – of the Partenopei’s whole season. Inter, we might remind ourselves, were second in late January of this year, before finishing 19 points clear in first place. Sunday’s avoidable collapse needs to be reflected on, but there are still positives to be found in a swaggering attack led by the ever-more confident Thuram.

Juventus remain a work in progress, a young team showing promise in some areas and naivety in others. Even with Yildiz on the bench, their starting XI against Inter was, with an average age of 25 years and 212 days, the youngest they have fielded in a Derby d’Italia since Opta started tracking data in 1994.

Not every clash between great sporting rivals needs to provide us with a singular narrative or sense of direction. Sometimes the best simply offer 90 minutes of marvellous entertainment – even if the manager disagrees.