Following in the footsteps of his older brother Alessandro, who had played for AC Milan since 1904, Attilio Trerè joined the Rossoneri in the following year. Since the team lacked a goalkeeper, the midfielder successfully adapted to the position, winning the league title in 1906. 12 months later, he was part of the title-winning side once again, playing in his natural position at midfield this time. He was conscripted into the Italian army in 1915, and an injury suffered in the trenches of Carso along the Isonzo river prevented him from returning to football once the war ended.
