Negro won the Coppa Italia during the 1997–98 season, also reaching the UEFA Cup final that year with Lazio, losing out to Inter. The following season, Lazio won the Supercoppa Italiana, and placed second in Serie A behind A.C. Milan, but won the 1998–99 UEFA Cup Winners' Cup, although he was an unused substitute in the club's 2–1 defeat of RCD Mallorca in the final. These successes were immediately followed by the UEFA Super Cup in 1999, defeating UEFA Champions League winners Manchester United in the final. During the 1999–2000 season, he helped Lazio win the Serie A title, with two goals in 26 appearances, also helping Lazio to capture the Coppa Italia and the Supercoppa Italiana over Inter, winning the first edition of the Pallone d'Argento in 2000. The prize is awarded to a player who has stood out during the course of a season, both for their discipline as well as for their footballing performances. Lazio also reached the quarter finals of the UEFA Champions League that season.