Sunday's 2-1 defeat inside the sold out Stadio Diego Armando Maradona was a flattering result for insipid Juventus, with Spalletti suffering his first defeat in eight games at the helm.
Of all the places to lose was heartbreaking for the 66-year-old, who celebrated winning the 2022/23 Scudetto with Napoli by having a tattoo of the club's crest on his left arm.
Yet the wily tactician, who only experienced a brief spell in charge of the Italy team, was to blame for the defeat because of his tweaks.
Expecting wingers Francisco Conceicao and Kenan Yildiz to lead the attack in the absence of Dusan Vlahovic, by overlooking Juve's only fit recognized strikers was a gamble that failed to pay off.
Jonathan David, a renowned goal poacher, arrived for the second half as an out-and-out forward but was ineffective. Unorthodox striker Lois Openda made a late appearance in place of Yildiz, who had been employed as a false no9, but like David failed to make an impact.
Yildiz found the back of the net just before the hour mark, sandwiched between the brace from Napoli's Rasmus Hojlund who is on loan from Manchester United. Yildiz added his name to the Juventus annals, as he became only the second player aged under 21 to notch at least five goals in the opening 15 Serie A games.
The 20-year-old Turkish talent joins the record books alongside his soccer hero Alessandro Del Piero, with the pair both sporting the iconic no10 Juve jersey.
Spalletti's seven-match unbeaten run had encompassed the Champions League, Coppa Italia and Serie A with three stalemates and four draws.
Spalletti senses problems with Juventus
He admitted to TV station DAZN Italia after the final whistle: "I feel Yildiz and Conceicao can do those roles [playing as forwards], as they pass the ball around well.
[Manuel] Locatelli sat a bit too deep and didn’t maintain the position I wanted in midfield. Then the two forwards had little mobility, and we kept getting bogged down in the middle. We didn’t pass it around quickly or make the numerical advantage count in midfield.
“Napoli pushed harder from the start. We were too timid moving the ball around, then lost it cheaply, so they made us run after them.
“They [Napoli] are in good shape. So if you don’t keep the ball, they make you run all over the pitch with their strength and quality.
“We did better in the second half as we went man for man, but still suffered with the pace and quality of the Napoli counterattack.
“After the equalizer we took control of the match. But again we were too obvious, too predictable. We didn’t try to do something extra, so we clearly need some progress and quickly, otherwise it becomes difficult.
Juve need better communication
“Napoli block to create space and we kept falling for it every time. We needed more communication, we made it also a bit easy for them to put the crosses in, these are all decisions that are made in the moment.
“We’ve done some good things [against Napoli], but we have reached a stage where we need to analyse the situation.
“Of course when the [Napoli] fans sing these songs that I know off by heart, it is spectacular, an atmosphere that only the Stadio Maradona can provide.”
“We can do better. as we gifted an incredible number of passes. If you don’t control the game, you end up being the passenger for the others making decisions for you.”