In the 1972 season, Mangual's batting average dropped to .246 with 5 home runs and 32 RBIs. His defense proved to be unreliable; he made 5 errors and Reggie Jackson ended up playing nearly four times as many games at center field as Mangual. Mangual won the first of three World Series rings that year, as part of the Athletics dynasty that won three consecutive championships between 1972 and 1974. During Game 4 of the 1972 World Series, Mangual hit a walk-off single in the bottom of the ninth inning against the Cincinnati Reds. It was the last of three pinch hits in that inning, setting a World Series record. The A's won that game 3–2 and took a 3–1 lead in the series. Mangual played his final major league game on June 20, 1976, at the age of 29. He finished his final season with a .167 batting average and one RBI in just 8 games. For his career, he batted .245 with 22 home runs and 125 RBIs in 450 games.
