Despite giving up a game-winning home run in his 1988 Opening Day debut at Fenway Park, Smith posted an ERA of 2.80 in 64 regular season appearances, his lowest ERA since 1983 (1.65). The Red Sox finished the regular season with a record of 89–73, good enough to win the American League East division, one game ahead of the Detroit Tigers. In Smith's second (and final) career trip to the postseason, he made two appearances in the AL Championship Series. Against the Oakland Athletics, he was the losing pitcher in Game 2, allowing the winning run via three ninth-inning singles. In Game 4, with Boston down three games to none and trailing 2–1, Smith allowed two insurance runs in the eighth inning as Oakland completed the series sweep.