There is an old theatrical tradition that a bad rehearsal is followed by a successful first night of a show.

Napoli must hope that this is true.

Sunday’s Serie A match against AC Milan was the first of three meetings between the two teams in 17 days. The other two are in the Champions League quarter-finals, with the first-leg match taking place in San Siro next Wednesday and the return match in Naples the following Tuesday.

Napoli hit a massive domestic league record during last night’s game, winning 11 of their 13 on their own patch this season and outscoring their opponents 33-9 in those matches, but they conceded twice in the first 25 minutes of a game for the first time. Since Luciano Spalletti was appointed coach almost two years ago and ended up losing 4-0.

It was Milan’s biggest league win this season and the first time in over seven years that anyone had scored four away goals in Serie A (Inter Milan 1 Fiorentina 4 September 2015).

The absence of Victor Osimhen with a thigh injury is too simple to explain Napoli’s defeat – they have won all seven matches they have played this season without their main striker before last night.

Coach Stefano Pioli’s tactical shift has returned, on paper, to a 4-2-3-1 system that won just one of six matches at the start of 2023, with his team conceding 17 goals in those matches.

Pioli said in late January that he would have been “foolish” if he had continued with this approach, switching to a 3-4-2-1 (as Milan defended with a 5-4-1); This led to five clean sheets in six matches, including the first leg of the Champions League last 16 against Tottenham Hotspur.

Pioli said before the Napoli match: “We tried both formations (three defense and four defense), we will choose the best.” In the end, they used both.

Milan defended the midfield 4-2-3-1, in the midfield of Napoli (most notably the yellow dots in this first screen).

With possession, Milan formed a defence-three, dropping midfielder Rade Krunic between or alongside the centre-back for overburdening Napoli’s attacking line. Spalletti pushed Piotr Zielinski forward from midfield to secure a 4-4-2 victory alongside Giovanni Simeone.

“We often left space between the lines, where it’s good; they have all these players who play half midfield… good midfielders… they found the man in the middle, we went to play man against man, we didn’t get along very well with centers”.

Milan kept the midfield balanced with Brahim Diaz, who lined up as a right winger but played like the number 10 on the back of his shirt. There he is on the left side of the field, receiving from guard Mike Minnan.

Rafael Leao, although he is right-footed than left-footed, is a more honest “winger” than Diaz. Milan left-back Theo Hernandez has been making upside-down runs to open up passing lanes from the three defenders to Leao.

Compare the positioning of Milan’s wingers (marked with yellow dots) and full-backs (black dots) against the Napoli midfield.

The build-up to Milan’s second goal – which Diaz scored – sums this up.

Hernandez’s walk inside opens the passing corner to Leao, who runs past Napoli’s midfield.

He dribbles the Portuguese winger and unites with number 9 Olivier Giroud.

Napoli’s four-legged defense is compact so Milan must go wide, with Liao finding midfielder Ismail Bennacer on his left.

Benasser’s cross – one of only six from Milan throughout the match (Napoli try 27) – is aimed at Giroud, but it looks at Napoli’s Kim Min-jae and the ball lands at Diaz’s feet.

Diaz, who is unmarked because left-back Mario Rui tried to influence Giroud’s jump …

… He stays still, cuts in – leaves Mario Roy on the floor – and doubles the lead.

Nine of Milan’s starting line-ups started last night in the 2-1 defeat at the San Siro in their September rematch – Leao was suspended, and Diaz came on as a second-half substitute. Pioli added their individual brilliance to a conditioning regimen that worked wonders.

Milan’s three-way style continued into the second half.

A short build, Krunic, from the right-back area, breaks the Napoli pressure with a diagonal pass to the left-back Hernandez in the central circle.

This exposes the Napoli defense quartet, once again, with Milan five against four, and they go from square to square in 14 seconds.

Hernandez works with Alexis Saelemaekers on Diaz as a replacement. His low cross reaches Giroud, who shoots straight at Alex Merritt but was offside anyway.

Milan showed versatility in their developing play – they would often run short and then go wide, either towards Giroud or Hernandez.

This led to Milan’s first chance of the night. Hernandez won the steal with a Mignan goal kick, then ran back to catch a backheeled pass for Liao…

… and pulled a low cross for Diaz, who forced Merritt to save – less than 12 seconds from the penalty area into the penalty area.

An early two-point deficit forced Napoli to expand. They were completely upset, and ran to take a corner in first half stoppage time.

Spalletti’s side were unsuccessful with a shot on goal before Milan scored their second, and when he did, it was defensive midfielder Stanislav Lobotka (two goals in 102 appearances since signing in January 2020) from almost 30 yards.

Milan used the medium and low blocks to reduce space for Napoli’s wingers and creative midfielders. The elected champions were forced to pass the ball and play big switches to wide areas – a less risky trick for Milan in Osimhen’s absence.

Here’s Giroud trailing gamely as a 36-year-old, making a fine ‘striker tackle’ in his defensive third position.

Midway through the second half, after conceding a corner kick, Fikayo Tomori signaled to his teammate that he needed to sit down instead of continuing to run side by side.

Milan, who has the most ‘direct attacks’, open plays (sequences that start only inside the team’s half, with at least 50 percent forward movement, and end with a shot or touch in the opponent’s box) in Europe’s top five leagues This season with 68, can now attack in the transition; This suited Leao, as he could lead in a disorganized defence.

Here, Maignan quickly distributes to Leao after claiming a cross, with Hernandez immediately making a center shot forward…

…and carried the play into the Napoli half, then moved to Diaz on the right…

…which dodges inside the box before it shoots.

Milan defended deeply, but the number of tackles (23) in the match was almost the same as the number of clearances (24), selecting his moments well to restore the midfield.

In January, pundit Paolo Di Canio – who played for both clubs, among others – described Milan midfielders Ben Nasser and Sandro Tonali as “the perfect tandem”. “She’s not very tall but her stride is quick. Tonali often runs with the ball and returns movement,” explained Di Canio.

Tonali shot high for the team, including the tackle that started the sequence that led to Milan’s third goal, Leo’s second. The 17-minute opener ended the club’s run of 11 games without Leo scoring and it was his first double since the 3-2 derby win over Inter in September.

Milan’s 34 percent possession in the second half was 10 percent less than in the first, but they had more shots (eight for six) and “great chances” (three for two). All five of their counter attacks, four of which ended in shots, came in the second half.

Napoli was self-destructive. The Silimmakers’ goal, Milan’s fourth and final on 67 minutes, summed up the game as he ripped through all four defenses and fired at Merritt.

Napoli may have the title in the bag by 16 points and 10 games left, but Milan last night showed their tough and adaptable side in their match that won the Scudetto last season.

Kick off the second act of this treble in the Champions League at the San Siro next week.