Sforza started his career in his hometown club
FC Wohlen. He was signed by
FC Aarau in 1989, where he impressed commentators and fans alike. Sforza's precocious talent was soon noticed, and he was signed by Swiss club
Grasshoppers Zürich one year later. He represented Grasshoppers during three successful seasons, also setting a record for the club as the youngest player to make his debut in the
Swiss Challenge League. Sforza became the general of the Kaiserslautern midfield and was recognised as one of the best midfielders in the German
Bundesliga championship, also receiving a
Ballon d'Or nomination in 1994, finishing in 21st place. During his time with Inter, Sforza became known for his inconsistency in
Serie A, and he is famously remembered in Italy for being referenced in the Italian film
Tre Uomini e una Gamba, by Italian comedic trio
Aldo, Giovanni e Giacomo; in the film, Aldo states that he had to purchase Sforza's number 21 Inter jersey as
Ronaldo's was out of stock. After a single season with Inter, he moved once again – but this time to known territory. In time for the
1997–98 season, Sforza moved back to Kaiserslautern where he immediately made an impression, experiencing a more successful stint with the club and finally demonstrating strong and consistent performances, which justified his reputation as one of the leading Swiss players of his generation. Even though Kaiserslautern had just been promoted from the
2. Bundesliga, Kaiserslautern became German champions, beating Sforza's other former team, German giants FC Bayern, to the title. Sforza spent two more seasons at Kaiserslautern, impressing commentators and fans alike. In 2000, he decided to give FC Bayern Munich another try. Once again, he failed to perform and spent a lot of time on the sidelines, although he later managed to participate in a more successful period with the club. FC Bayern had many star players competing for places, and the team won both the
2000–01 Bundesliga and
2000–01 UEFA Champions League titles that season. After two seasons at Bayern, he returned to Kaiserslautern for a third spell in 2002. The aging and now somewhat injury-prone Sforza helped FCK avoid
relegation, however, in October 2005, he had a public falling-out with the club and was blackballed. He retired at the end of the season, in summer 2006. ==International career==