He made his Serie A debut with the club during the end of the 1965–66 season, on 18 September 1966, in a 2–1 win over Venezia, but was briefly loaned to Serie B club Savona during the 1966–67 season. He later helped Milan to win the 1967–68 Serie A title, finishing the season as the top goalscorer in the Italian league, with 15 goals. He was also notably part of their European Cup victory in 1969, scoring a hat-trick in the 4–1 defeat of Ajax in the final, and six goals in total throughout the competition. He is the last man to have scored a hat-trick in the Champions League/European Cup Final. Ferenc Puskás (twice) and Alfredo Di Stefano (both of Real Madrid) are the only other players to have achieved this.