In the postseason, the Orioles faced the Twins in the newly created best-of-five AL Championship Series, the winner of which would play in the World Series. McNally threw nine shutout innings in Game 2, limiting the Twins to three hits, but the Orioles were unable to score, and the game continued. Still on the mound, McNally threw a hitless 10th inning. With two outs in the top of the eleventh, he walked Harmon Killebrew and Tony Oliva to put a runner in scoring position before getting Bob Allison to line out to Don Buford in left field. Curt Motton finally drove in a run in the bottom of the inning, and the Orioles prevailed 1–0. McNally's shutout is the longest by a pitcher in the postseason, and Will Leitch of "MLB.com" called the game the Orioles' most exciting playoff victory in 2018. The Orioles faced the New York Mets in the 1969 World Series. In Game 2, the Orioles and Mets were tied at one in the ninth when McNally, with two outs, gave up three singles in a row to give the Mets a 2–1 lead. The two runs were all he allowed in the ballgame, but the Mets prevailed 2–1. He hit a two-run home run against Jerry Koosman in Game 5 and left the game after seven innings with the score tied at three. However, the Orioles lost the game 5–3, and the Mets won the World Series in five games.