Dietz was an integral member of the 1971 Giants team that clinched the National League Western Division title. The Giants had a nine-game lead over the Los Angeles Dodgers on August 1, but held on during a pennant race to win the division by a narrow one-game margin. Dietz caught every game during the tense final stages of the season, and provided offensive support with 19 home runs and 72 runs batted in. In the only post-season appearance of his career, Dietz had only one hit in 15 at-bats, as the Giants lost to the eventual world champion Pittsburgh Pirates in the 1971 National League Championship Series.