After attracting attention from larger clubs, he joined Juventus in 1993 for 11 billion Lit., featuring as a starter during the 1993–94 season under manager Giovanni Trapattoni.
In particular, Porrini was kept out of the starting eleven by the newly acquired Ciro Ferrara, whom Lippi had even moved onto the right flank in order to accommodate him into the team's new back-line.
Despite his limited appearances for Juventus during the season, Porrini still proved to be decisive for the team: he notably scored two goals over both legs of the club's 1995 Coppa Italia Final victory over Parma,[2] as well as a crucial goal in a 2–1 home win against Borussia Dortmund, in the second leg of the semi-final of the UEFA Cup, helping his team to reach the final of the tournament, where Juventus lost out to Parma; he captured his first Serie A title with the club that season.
He started off his Rangers career at centre-back alongside Richard Gough but new manager Dick Advocaat soon moved him to right-back where he remained until he left the club in 2001.
[1] While at Juventus, Porrini gained two international caps for Italy in 1993, under manager Arrigo Sacchi, appearing in two 1994 FIFA World Cup qualifying matches.