Westrum was a key player for the Giants’ during the remarkable pennant race in which the Giants, 13 games behind the Brooklyn Dodgers on August 12, fought back to win 16 games in a row and finished the season tied with the Dodgers for first place. His two-run, eighth-inning home run against Ralph Branca on August 13 snapped a 1–1 tie and gave the Giants a 3–1 victory over the Dodgers. Westrum contributed 20 home runs with 70 runs batted in, and led National League catchers in baserunners caught stealing. The two teams met in the 1951 National League tie-breaker series in which the Giants' season was climaxed by Bobby Thomson's "Shot Heard 'Round the World", a three-run home run in the bottom of the ninth inning for a 5–4 win of the third and final playoff game. Afterwards, the Giants would lose to the New York Yankees in the 1951 World Series.