Starting Game Two of the World Series against the Boston Red Sox, Wacha pitched six innings in a 4–2 Cardinals' victory, although he said after the game he "didn't have [his] best stuff." Before surrendering a home run to David Ortiz, Wacha tied Gibson with the longest scoreless streak (19 innings) in Cardinals' postseason history. Wacha became the 17th-youngest pitcher overall to win a World Series game and the second-youngest in Cardinals history behind only Paul Dean. In Game 6, with the Cardinals facing elimination once more, Wacha was again called upon to save their season after winning four consecutive playoff starts with a 1.00 earned run average and just 11 hits allowed in 27 innings for a .122 opponents' batting average. However, the Red Sox finally solved him, tagging him for six runs in innings on their way to defeating the Cardinals for their eighth World Series title.