It was, as Marco Materazzi says, the moment when "everything changed" for Inter.
Alexis Sanchez lost possession in midfield. Sandro Tonali started an AC Milan counterattack.
And then Olivier Giroud diverted home a deflected shot from Brahim Diaz to level the Derby della Madonnina.
An ugly goal, for sure, but also a hugely significant one, not only in the context of the game, but the entire Serie A season.
"It was as if something just switched off," Materazzi told the Gazzetta dello Sport. "Fear returned, [Inter] lost confidence."
Indeed, just three minutes later, Giroud scored again to complete the unlikeliest of comebacks. After all, Inter had dominated the preceding 75 minutes of their February 5 meeting with Milan.
The then-league leaders were full value for the first-half lead given to them by Ivan Perisic's wonderfully well-taken volley.
The reigning champions looked destined to move seven points clear of second-placed Milan having played one game fewer.
The Scudetto race would have been effectively over had they held on.
Now, though, almost exactly two months on, it is Inter whose title hopes are hanging by a thread.
Inter had won nine of their previous 10 league games going into the derby.
They've managed just one victory since, at home to the weakest team in the league, Salernitana.
Taking just seven points from their last seven games has seen them not only fall behind current table-toppers Milan (-6), but also Napoli (-3).
Worse still, they are now just one point ahead of fourth-placed Juventus, whom they face in Turin on Saturday night.
They still have a game in hand but defeat in the Derby d'Italia would render it almost irrelevant in the context of their Scudetto bid, particularly with Milan hosting Bologna on Monday night.
The result, then, will have a massive bearing on Inter's title defence. However, it could also impact their coach's future at San Siro.
According to Saturday's Gazzetta, "Inzaghi risks it all" at Juventus Stadium.
A loss would reportedly prompt Inter to evaluate whether the former Lazio boss is really the right man for the San Siro hotseat, with doubts mounting over his tactical versatility and ability to effectively rotate his squad.
Inzaghi, of course, needed no reminding of the importance of the game, having already pointed out that Inter now need to win "nine finals, starting on Sunday, which is certainly the most challenging".
There's no disputing that claim. So strong is the rivalry between these two sides, Juve would have been desperate to beat Inter anyway. But this is an absolutely colossal game for the Bianconeri too.
GettyCoach Massimiliano Allegri continues to insist that Juve are still too far behind to be considered Scudetto contenders – they trail Milan by seven points – and says their focus is on strengthening their grip on a Champions League place.
However, a Derby d'Italia triumph would send a clear signal that the Old Lady are perfectly poised to take advantage of any slips from the top two.
Juve have undeniably been tough to watch this season, but they are also now proving difficult to score against – no Serie A side has kept more clean sheets (13).
The return of their famed backline brilliance has played a key role in them putting together the longest unbeaten run in Europe's 'Big Five' leagues (16 games), allowing them to make up 10 points on Inter over the past nine matchdays.
The arrival of Dusan Vlahovic has obviously also been key, with the prolific Serbian taking next-to-no time to settle in Turin, thus adding a whole other dimension to their attack, as well as inspiring an upturn in Alvaro Morata's efficacy.
Of course, doubts persist about the quality of Juve's midfield, and its ability to control a game.
In that context, the return of Marcelo Brozovic could not have come at a better time for Inzaghi, particularly with Nicolo Barella showing serious signs of fatigue in recent weeks.
Inter are simply not the same side without the Croatian, whose recent contract extension came as a massive boost to the club, and it's no coincidence that he missed three of the last four games in which they have dropped points.
Getty"[Brozovic is important] not only for the technical qualities, but also for the aerobic ones," former Inter defender Beppe Bergomi told the Gazzetta. "He runs constantly and everywhere, and always shows for the ball.
"He reminds me of [Gianluca] Matteoli, who once said to me 'Beppe, don't be afraid to give me the ball even if I have an opponent attached to my backside!'
"It is essential players like this who make teams tick."
There is an undeniable feeling, though, that this latest meeting between these two great rivals will be more about mentality than tactics.
Allegri has been here many times before. He already has six Scudetti to his name.
Inzaghi, by contrast, has yet to win one. He went close with Lazio in 2019-20 but their challenge eventually fell apart around this stage of the season and the Romans ended up finishing fourth.
He has yet to prove, then, that he has what it takes to handle the pressure of what is essentially a Scudetto eliminator.
As Fabio Capello pointed out in the Gazzetta, "Even a draw would be like a defeat for both sides."
Nothing less than a victory will suffice, especially for Inzaghi. His job may depend on it.
He really will have to risk it all at Juventus Stadium on Sunday night.