Rubuta ci gaba don wannan sakin layi - A kakar wasa ta gaba, Riva ya fara buga wasan farko a Serie A don Cagliari a ranar 13 ga Satumba, 1964, a cikin rashin nasara 2<unk>1 da Roma, kuma ya kuma taimaka wa kulob din kauce wa saukewa, yana jagorantar ƙungiyar zuwa matsayi na shida a cikin teburin, inda ya zira kwallaye 9 masu ban sha'awa a wasanni 32 a lokacin da yake da shekaru 20. Wannan ya biyo bayan matsayi na goma sha ɗaya, na shida, da na tara a cikin gasar tsakanin 1965 zuwa 1968, yayin da Riva kuma ya gama a matsayin dan wasan da ya fi kowa zira kwallaye a karon farko a kakar wasa ta 1966-67 tare da kwallaye 18, yayin da kulob din ya fara gina wata kungiyar da za ta iya lashe gasar a kusa da tauraron dan wasan su: Riva ya jawo hankalin 'yan wasan kwallon kafa da yawa zuwa Cagliari, kuma kungiyar a wannan lokacin tana da manyan' yan wasa kamar Enrico Albertosi, Roberto Boninsegna, Ricciotti Greatti, Comunardo Niccolai, Mario Martiradonna, Mario Brugnera, Pierluigi Cera, da Nené. Riva daga baya ya taimaka wa Cagliari zuwa matsayi na biyu a duka Coppa Italia, a bayan Roma, da kuma gasar, maki hudu a bayan Fiorentina, a lokacin kakar 1968-69.
Cagliari ya jagoranci gasar har zuwa ranar wasa na 21, lokacin da rashin nasara a gida ga Juventus ya sa ƙungiyar ta ba da jagorancin ta.