On August 16, 1920, Mays threw the pitch that fatally injured Ray Chapman of the Cleveland Indians, the only major league player to die as a direct result of an on-field injury.

His best personal support group was a couple named Pierce and Genevieve Mays, who were relatives and served as a surrogate uncle and aunt.

In part because of his strict Methodist upbringing, Mays refused to pitch on Sundays, as did legendary pitcher Christy Mathewson.

[7] Mays quit high school before graduating and began to earn a living as a baseball player on semi-pro teams in Oklahoma, Kansas, and Utah.

[5] In one version of the story, Mays learned his underhand style of pitching from Dizzy Dismukes, a pitcher in Negro league baseball.

Mays was also known for a habit of throwing inside to any batter who hugged the plate; despite a stellar win–loss record, he was typically among the American League leaders in hit batsmen.

In the eighth inning, after another close pitch, Cobb threw his bat in Mays' direction, calling him a "no good son of a bitch".

[14] After a brief honeymoon in Missouri, he departed by train from his home in Mansfield for St. Louis as the leader of a group of 18 men who had enlisted in the United States Army for World War I.

However, that same season Mays, pitching for the Yankees, played in a World Series that others later accused him of helping to throw, bringing back memories of the Black Sox scandal from just two years prior.

These rumors were never proven, but they persisted long enough that, combined with an already negative reputation among other players both from the Chapman incident and from having a personality that few found agreeable, he was never elected to the Baseball Hall of Fame despite having lifetime statistics comparable to some other pitchers who were.

Mays is the only Red Sox pitcher to toss two nine-inning complete game victories on the same day, as he beat the Philadelphia Athletics 12–0 and 4–1 on August 30, 1918.

[23] Those wins put the Red Sox one step from clinching the league championship, as they led Cleveland by 3+1⁄2 games with four remaining to play.

After his playing career, Mays was the owner and operator of a baseball school in Oregon; among his most notable attendees was Johnny Pesky.

In an interview, Mays said he especially enjoyed working with young pitchers, but that he regarded his most important task as teaching members of the team how to play the game safely.

After the 1918 World Series, Mays married Marjorie Fredricka Madden, a graduate of the New England Conservatory of Music whom he had met during his rookie season.

In August 2008, Mays was one of the 10 former players who began their careers before 1943 to be considered by the Veterans Committee for induction into the National Baseball Hall of Fame in 2009.

[citation needed] In 2021, indie-folk artist Cousin Wolf released a song entitled "Carl Mays" as part of an album called Nine Innings.