Kammala jumla mai zuwa: An haife shi a Pisa, Galli ya fara aikinsa tare da matasan garinsa a matsayin dan wasan tsakiya kafin ya sauya zuwa matsayin mai tsaron gida. Ya fara aikinsa na sana'a tare da ACF Fiorentina a 1977, inda ya buga wasanni tara a Serie A. A cikin
A 1986-87, ya koma kungiyar A.C. Milan, inda ya zama na farko a cikin shekaru uku daga cikin shekaru hudu, kuma ya kafa kansa a matsayin daya daga cikin masu tsaron gida mafi kyau a Italiya, inda ya lashe gasar Serie A da Supercoppa Italiana a kakar wasa ta farko. Ya kuma fara farawa a duka nasarar da kungiyar ta samu a gasar cin kofin Turai, a shekarar 1989 da 1990, kuma ya lashe gasar cin kofin Turai a 1989 da 1990, da kuma gasar cin kofin Intercontinental a shekarar 1989. Ya kuma kai wasan karshe na 1989-90 Coppa Italia tare da Milan. A lokacinsa na ƙarshe tare da kulob din, sau da yawa ana canza shi kuma yana fuskantar gasa don farawa daga Andrea Pazzagli, wanda manajan Arrigo Sacchi ke yawan buga shi a lokacin wasannin gasar, yayin da Galli ya buga wasannin Turai.