Alessandro Costacurta was affectionally known to his fans as "Billy", due to his thin physique in his youth, and his notable skill at basketball (as the local basketball team of Milan, Olimpia Milano, was referred to as "Billy" during the late 1970s, the team's main shirt sponsor). Originally an AC Milan youth side product, during his professional career Costacurta would go on to play for the senior club for over 20 seasons, after a brief spell on loan at Monza in Serie C1 during the 1986–87 season. Costacurta was already a young member of the senior squad during the 1985–86 season, but failed to make a single appearance. Before being sent to Monza on loan, Costacurta would make his Milan debut in the Coppa Italia during the 1986–87 season, but would not make his Serie A debut with Milan until the following year, under Arrigo Sacchi. Costacurta made his first Serie A appearance on 25 October 1987 against Hellas Verona on the sixth matchday of the season. Milan would go on to win the match 1–0, as well as the Serie A title, but Costacurta received limited playing opportunities that season, due to the presence of the more experienced Filippo Galli in his position. Overall, Costacurta managed 7 appearances in Serie A, and one appearance in the Coppa Italia that season.