Simone Inzaghi could not allow himself to celebrate right away. The Rome derby was 12 minutes old when Felipe Caicedo rounded Robin Olsen and rolled home the opening goal at the Stadio Olimpico. While the forward hurdled the advertising hoardings and sprinted towards an adoring public, Lazio’s manager turned towards the nearest official to double-check that this strike would stand.

A sign of the times in Serie A? Every goal is reviewed automatically by the VAR booth, and we have seen plenty of high-profile reversals in recent weeks. Inzaghi has been a vocal opponent of the technology in the past, contending that it “takes away the emotion” of football.

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Perhaps, on this occasion, his hesitation stemmed also from disbelief. Could it really be this easy to carve through Roma’s defence? There was no obvious danger when Luis Alberto took a throw-in by the halfway line, but he sent the ball to Joaquín Correa, who split Federico Fazio and Juan Jesus with the gentlest of through-balls. Caicedo had time to run around the back of the Brazilian before advancing, unchecked, on the keeper.

It was easier for Inzaghi to let loose by the 89th minute, when Danilo Cataldi made it 3-0 to Lazio. The midfielder was left unmarked on the edge of the area, where he received a lay-off from Sergej Milinkovic-Savic before curling a shot across his body and into the right-hand corner of the net.

Ciro Immobile had padded Lazio’s advantage with a penalty in-between. Once again, Roma’s defending was poor. Fazio allowed Correa to get behind him too easily and waited until his opponent had broken into the box before bringing him down.

Inzaghi’s tactics had helped to put Roma on tilt. His decision to drop Immobile from the starting XI came as a surprise, with Caicedo instead lining up ahead of Correa in a 3-5-1-1. Luis Alberto also replaced Marco Parolo in central midfield, and together with Milinkovic-Savic he gave the team a wealth of attacking options.

Facebook Twitter Pinterest Roma’s Aleksandar Kolarov in the back of the net after failing to stop Felipe Caicedo’s opener crossing the line. Photograph: Alberto Lingria/Reuters

The right wing-back, Adam Marusic, was instructed to push forward, obliging Aleksandar Kolarov to retreat. Bastos then moved from centre-back to occupy any space that Stephan El Shaarawy might have found as a result.

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The idea was to force Roma to play down the opposite flank, which they duly did. There Nicolò Zaniolo, so impressive in this campaign to date, was made to look like the inexperienced teenager that he is by Stefan Radu and Senad Lulic. He lost possession 13 times before being subbed off in the 61st minute.

It was a plan devised inside four days by Inzaghi, following a midweek Coppa Italia draw with Milan. The Lazio manager cut back his players’ time on the training ground in favour of extended film review sessions: a decision which paid off as his team dominated the opening exchanges.

Roma did adjust, manager Eusebio Di Francesco amending his initial 4-3-3 to a 4-2-3-1 late in the first half before sending on Diego Perotti and Javier Pastore after the interval. The latter fluffed a golden opportunity to level the scores at 1-1, firing wide of the far post after an Edin Dzeko knock-down five yards from goal.

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And yet, you could not say they were unlucky. To do so would excuse gross negligence in their defending: not only from the players but the manager himself. An initial midfield three of Lorenzo Pellegrini, Bryan Cristante and Daniele De Rossi was always going to be vulnerable against fast-breaking opponents – with the former two players inclined to get forward and the latter no longer athletic enough to cover for them.

Roma were missing their best centre-back, Kostas Manolas, due to illness, yet he has not been able to save them from calamity on other occasions this season. He played the full 90 minutes as they were thrashed 7-1 in the Coppa Italia by Fiorentina this January. Of the teams in the top-half of the Serie A table, only Atalanta have conceded more goals (37) than the Giallorossi (36).

Facebook Twitter Pinterest Rome native Danilo Cataldi (right) scored Lazio’s third goal. Photograph: Angelo Carconi/EPA

Is this an issue of management, or recruitment? Roma’s directors met to discuss Di Francesco’s future after the defeat on Saturday night, and a failure to progress beyond Porto in the last-16 of the Champions League on Wednesday (the Italians lead 2-1 from the first leg) could yet cost him his job.

There has been criticism of Monchi too. Why were no centre-backs added in January, despite a glaring lack of quality at the position? Ought the Spaniard to have put more thought into the question of midfield balance during a summer recruitment phase when a great many talented young players arrived, but too many of them with similar profiles?

Di Francesco confessed at full-time on Saturday to being worried about his team’s trajectory. A win here would have moved Roma level in fourth with an Inter side distracted by the Mauro Icardi saga. Instead, Lazio could now move pull alongside the Giallorossi in fifth if they win their game in hand.

More impactful still might be the simple fact of losing a derby by such a wide margin. Lazio had won only two of the previous 13 head-to-heads. They had not beaten Roma by three goals since December 2006, when their manager, Delio Rossi, celebrated by diving into the giant fountain – Il Fontanone – on Rome’s Janiculum hill.

Inzaghi was quick to dismiss a suggestion he might follow suit, but hailed this as a night that would live long in Lazio’s history. The fact that it was capped by a goal by Cataldi – a Rome native and former captain of the youth team – felt especially fitting.

“I thanked my players because they were magnificent,” said the manager. By full-time, even he could feel free to celebrate.

Talking points

• Juventus are 16 points clear and will win an eighth consecutive Scudetto. But were there many other positives for them to take from their win away to Napoli? They played with an extra player for almost 40 minutes, but still finished with 36.5% of possession. From two goals and a man up, they came within a missed penalty of drawing (or worse). Juventus’s season was always going to be defined by their efforts in the Champions League. There was little in this display to suggest they can overturn a 2-0 deficit against Atlético next week.

• The anniversary of Davide Astori’s death was marked by a pause for applause in the 13th minute of each game this weekend. It was moving to see how players were affected – Josip Ilicic wept in Bergamo as he remembered his former teammate during Atalanta’s win over Fiorentina.

Facebook Twitter Pinterest A minute’s silence is observed for Davide Astori at the Stadio San Paolo. Photograph: NaFoto/Action Plus via Getty Images

• That was the second meeting in four days between Fiorentina and Atalanta, who also faced off in the Coppa Italia on Wednesday. Just the 10 goals between them, with a second leg still to come next month.

• Mauro Icardi broke his silence with a long letter on Instagram in which he emphasised the loyalty he believes he has shown to Inter, while questioning whether he had received fair treatment. Meanwhile Inter’s defeat to Cagliari has raised the stakes as they slipped behind Milan into fourth.﻿