Rafael Leao raced clear to open the scoring with just over six seconds on the clock, giving Milan a dream start, before Alex Saelemaekers doubled their lead midway through the first half.
A late Domenico Berardi freekick made for a nervous ending, but the Rossoneri held firm at the Mapei Stadium to end a run of consecutive draws and remain top of the table.
Lightning Leao goes into history
Blink and you’d miss it, such was the pace of Milan’s start to proceedings on Sunday. Straight from kick off, Hakan Calhanoglu drove forward and released Leao with a sumptuous through ball for the Portuguese to slot home, before Sassuolo had even come close to getting a touch.
Leao’s goal saw him break Paolo Poggi’s record that had stood for 19 years after he netted in eight seconds for Piacenza against Fiorentina in December 2001, and the forward can hope to hold the record for just as long.
It was no less than Milan deserved after dominating the opening half hour, and with their lengthy unbeaten run in Serie A and goalscoring streak extending ever further, the Rossoneri are worthy of going down in the history books.
Suggestions of fatigue are premature
It has been a gruelling campaign for all teams in Serie A, not least Milan with their European commitments, including qualification rounds for the Europa League.
With a squad hit hard by injuries to the likes of Zlatan Ibrahimovic, Ante Rebic and Simon Kjaer, their imperious form took a knock with consecutive 2-2 draws against Parma and Genoa respectively, requiring late equalisers in both.
It has led to suggestions in some quarters that Milan are in danger of burnout and their slick play is catching up with them as fatigue sets in, but their was no sign of that in Reggio Emilia.
Flying out of the traps, Milan were on top in the first half whilst also adept at soaking up pressure and launching lung-bursting counterattacks, as seen by Theo Hernandez’s charge up field to tee up Saelemaekers.
Sassuolo dominated possession to the tune of 68%, but the Rossoneri were resolute in defence and more than capable of turning defence into attack at the blink of an eye.