He enjoyed his highest win season in 1924 with the seventh-place Red Sox, when he won 14 games while losing an American League-high 17.

In 1925 he divided his playing time with Boston, New York and Washington, ending with a 5–1 mark and a 3.25 ERA in seven games for the Senators AL champion team.

In a 10-season career, Ferguson posted a 61–85 record with 397 strikeouts and a 4.89 ERA in 257 appearances, including 166 starts, 62 complete games, two shutouts, 10 saves, and 1241+2⁄3 innings of work.

In 1926 Ferguson set a major league record for the highest ERA during a regular season by a pitcher who started a postseason game the same year.

The mark was broken in 2006 by Óliver Pérez of the New York Mets, who posted a 6.55 ERA during the regular season before starting Game 4 of the NL Championship Series.