Fuentes returned to the Giants in 1969 and spent the next two seasons as a utility infielder before re-gaining his starting spot at second base in 1971. He appeared in the postseason during the 1971 season as his Giants won the NL West title; his two-run home run in Game 1 of the 1971 NLCS helped San Francisco take an early series lead against the Pittsburgh Pirates, but that would turn out to be the Giants' only win of the best-of-five series. Fuentes continued to be the Giants' second baseman for three more seasons. In 1973, he set a National League record by recording a .993 fielding percentage, the highest for any regular second baseman in league history. Ironically, Fuentes had led all National League second basemen in errors during the previous two seasons before setting the new record for excellence. His record stood for 13 seasons before Ryne Sandberg recorded a .994 percentage at second in 1986.