Despite his talent and goalscoring prowess, Riva's career was blighted by several major injuries, in particular with the Italian national side, and which greatly limited his playing time in later seasons; he missed 35 games in the five seasons leading up to 1971, and only appeared in 24 matches for Cagliari between 1974 and 1976, which saw an overall decline to his goalscoring rate and the club's performances during this period. During the 1974–75 season, a calf injury limited him to 8 appearances and 2 goals with the club, and on 1 February 1976, while playing in a match for Cagliari against Milan, Riva ruptured a tendon and tore an adductor muscle in his right thigh, following a physical shoulder challenge near the corner flag from Aldo Bet, after being chased down by the Milan defender; he never successfully recovered and, despite several comeback attempts over the next year and a half, was eventually forced to retire in 1978, at the age of 33, having played his last game at the age of 31 in 1976. The injury limited Riva to only 15 appearances during the 1975–76 Serie A season; despite his run of six goals in a span of eight games during the final season of his career, Cagliari finished in last place in the league in his absence, and were relegated to Serie B. In total, Riva scored 248 goals for club and country throughout his career in 439 appearances, scoring 164 league goals with Cagliari in 315 appearances, 156 of which came in 289 Serie A appearances. Overall, he scored 207 goals in 374 appearances in all competitions during his thirteen seasons with Cagliari, and 213 career club goals in 397 appearances.