Born in Snohomish, Washington, Averill broke into the Major Leagues in 1929 (at the age of 27) with the Cleveland Indians. He played for Cleveland for over ten years, and remains the all-time Indians leader in total bases, runs batted in, runs, and triples. He also remains third in all-time Indians hits and doubles, and fourth in all-time Indians home runs and walks. During his time in Cleveland, the team never finished higher than third. His nickname was “The Earl of Snohomish”. He famously hit the line drive that broke Dizzy Dean’s toe in the 1937 All-Star Game. Dizzy, who had averaged 24 wins a season up to then, and only 4 wins a season after, changed his delivery due to the broken toe, damaged his arm, which led to his retiring in 1941 at the age of 31. Averill was the first Major League player to hit four home runs in a doubleheader (three home runs in first game, one in second game) on September 17, 1930; he was also one of the first players to hit a home run in his first Major League at-bat (April 16, 1929, opening day). Averill batted .378 in 1936, leading the American League in hits with 232, but finishing second to Luke Appling in the batting race (Appling batted .388 for the White Sox).

During a July 1st incident in 1935, Averill was lighting firecrackers with his four children as part of a pre-July 4th celebration. One exploded while he was holding it, and he suffered lacerations on the fingers of his right hand, as well as burns on his face and chest. After several weeks, he made a full recovery.

In 1937, Averill experienced temporary paralysis in his legs and was diagnosed with a congenital spine condition. This caused him to alter his batting style and become less of a power hitter.

In 1941, Averill struggled with the Boston Braves and was released on April 29th. He wound down his pro career in the Pacific Coast League with the Seattle Rainiers.

After his career, he was very outspoken on being elected to the Hall of Fame. While he did not campaign for induction, he did make the statement that, “Had I been elected after my death, I had made arrangements that my name never be placed in the Hall of Fame.” Averill was inducted in 1975, eight years before his passing.