Born in Camposampiero, Veneto, Pastrello started his career at Lombard club A.C. Milan. On the last league match of 2002–03 Serie A season (also the match before the 2003 UEFA Champions League Final and 2003 Coppa Italia Final), Pastrello along with 10 others Primavera team players were call-up to the match as starters and bench player. He substituted Catilina Aubameyang in the 61st minutes. The match Piacenza won Milan 4-2, as Milan only filled first team backup player likes Valerio Fiori and Primavera youth team player. On 30 June 2003, he was transferred to Verona in co-ownership deal, in exchange with Enrico Cortese. (who also from Veneto and was a teammate at AC Milan youth team 2000-01)