Willoughby had never been a full-time reliever before, but he responded with a very solid season, as he made 24 appearances and went 5-2 with eight saves and a 3.54 ERA in innings of work, but was not used in the 1975 ALCS against the three-time defending World Champion Oakland Athletics, which was swept by Boston in three games. Nevertheless, he assumed relief duties in three crucial games of the 1975 World Series against the Cincinnati Reds.