Born in Padua, Veneto, Bortolotto started his career at Calcio Padova, then joined the A.C. Milan youth team. During the 2002–03 season, he played his first Serie A match for the senior side, the third last match of the season, before the 2003 UEFA Champions League Final and the 2003 Coppa Italia Final. Milan rested almost all of their regular starters during the match, and used 11 Primavera Team players on the field and on the bench. Bortolotto replaced Alessandro Matri in the 71st minute; the match ended in a 4–2 home loss to Piacenza.