Marcus Thuram excels in his first Milan derby, Henrikh Mkhitaryan scores a brace in the two key moments of the match and Hakan Calhanoglu certifies the victory with a penalty before Davide Frattesi's pearl: with these ingredients, Inter asphalted Milan, taking the place of first of the ranking.
Both teams came to the derby with high morale, after the start of the championship with three wins each, however, it only took 5 minutes for the derby to turn black.
A quick drop by Marcus Thuram on the right wing, a pass to Mkhitaryan and the Armenian sends the ball into the net, sparking a celebration at San Siro filled with around 70,000 Inter fans.
Milan tried the reaction and Theo went close to the equalizing goal, but after a model action, he shot easily and wide. Then comes another Inter breakaway, with Thuram doing everything right before unleashing a perfect right-hander to send the ball into Mike Maignan's triangle.
The first half ended with the double advantage of the black and white, as the 45-minute second started amid heavy rain and the desire for reaction on the part of Milan, who reopened the meeting with Leaon in the 58th minute. The Portuguese forward was well served by Giroud and used his speed to score Yann Sommer's first goal of the season.
But the Reds and Blacks' enthusiasm fades quickly, as in the 69th minute, Inter make another quick descent, with few passes, and Mkhitaryan scores his second personal goal and the third for Inter, helped by Loftus-Cheek's deflection.
In the 79th minute, Theo Hernandez intervened with a delay against Lautaro, causing a penalty, as Hakan Calhanoglu went from the penalty spot, scoring the former's goal, but also the fourth for the Zikatlr.
The celebration was completed in extra time by Italy's man of the moment, Davide Frattesi, who after scoring twice against Ukraine four days earlier, had another in the derby to complete a convincing 5-1 win.
After this challenge, Inter climbs to the top alone, with 12 full points, while Milan remains in second place, with 9 points and with a lot of work to do in order to put this defeat behind them.