During his rookie 1903 season, Gibson was the fourth man of a Boston rotation that included Cy Young, Bill Dinneen, Long Tom Hughes, George Winter and Nick Altrock. He responded with a 13–9 mark, 76 strikeouts, and a 3.19 in innings pitched. He thus won a World Series ring as a member of the Americans that won the first World Series that season, although Gibson did not play as Collins used only three pitchers, Young, Dineen and Hughes, for the entire series. His second season was much better, when he recorded 17 wins, 112 strikeouts, a 2.21 ERA and 273.0 innings, all career-highs, as his .592 winning percentage ranked him seventh between American League pitchers. The next two years, his playing time was limited by arm injuries. He retired after the 1906 season.