AC Milan suffered a disappointing 3-0 loss at the hands of Atalanta in Serie A on Saturday evening.
Milan named Fikayo Tomori and new signing Mario Mandzukic on the bench following their arrivals during the course of the week.
It was Atalanta who took the lead early in the first half through Cristian Romero before a penalty in the second half from Josip Ilicic gave them a second.
Duvan Zapata put the home side to the sword as the match headed towards the end, as Milan picked up their second defeat of the season.
Inter Milan disappointingly failed to close the gap at the top of the table with a goalless draw away to struggling Udinese in Udine.
Following last Sunday's victory over Juventus in the Derby d'Italia, the Nerazzurri were buoyant from the start but a number of missed chances from particular Lautaro Martinez proved their undoing.
Head coach Antonio Conte was sent off for dissent late on as frustrations started boiling over for the second-place Nerazzurri who settled for a point in the end.