After only three league appearances for Milan, he was loaned out to Empoli for the rest of the 2002–03 Serie A season. He returned to Milan for the entire 2003–04 season, but played in just four league games. In the 2004–05 season, he was on loan at Reggina. In the 2005–06 season, he was once again sent on loan, this time to Sampdoria along with Milan teammates Samuele Dalla Bona and Ignazio Abate. Borriello left Sampdoria in January 2006 for a six-month loan stint at Treviso where he scored his then-career best of five Serie A goals. Treviso, however, were relegated to Serie B that season.