De Sciglio explains when he realised Milan exit was inevitable: "Boos rained down"

"De Sciglio first appeared on the big scene in the 2011-12 season, making his debut in the Champions League (of all competitions) for Milan. He quickly proved to be a versatile defender, able to play on each flank and in the centre if needed. Naturally, he was a player that Massimiliano Allegri liked a lot and that resulted in a lot of playing time during the 2012-13 season."

"I was angry. It was a substitution I never understood. It seemed like he wanted to use me as a scapegoat to shift attention from the entire team's difficulties. As I was leaving the pitch, a hail of boos rained down on me from the stands. That day, I realised I couldn't continue like this: my story with Milan was over,"

Mattia De Sciglio emerged in 2011-12 with a Champions League debut and established himself as a versatile defender capable of playing both flanks and centrally. Massimiliano Allegri trusted him, producing significant playing time in 2012-13. He remained a key squad member through managerial changes and left for Juventus in summer 2017. An injury undermined his consistency and led to a run of poor performances. A substitution during the April 23, 2017 match against Empoli triggered boos from supporters and left him feeling scapegoated, prompting him to conclude his time at Milan was over.

Read at SempreMilan