In 1901 Mordecai, with the help of six hundred fans who threatened to boycott the games if he didn't make the team, secured a spot on the Terre Haute Tots (or Hottentots) in the newly formed Three-I league. Mordecai led the semiprofessional team to the first-ever Three-I championship, posting a 23-8 record.

Mordecai was picked up by Omaha in the Western League the following year, and reporters started calling him Three Finger. He became the staff workhorse, posting a 27-15 record and finishing every game he started.

After that season in Omaha, Mordecai joined the St. Louis Cardinals in 1903. His major league debut for St. Louis, against Chicago of the National League, was similar to the outing in Coxville. In both games Brown pitched five innings, and his dominance over hitters was obvious to all observers. While his rookie record was not impressive, 9-13, it should be remembered that St. Louis was the last-place team that year in the National League, 46 1/2 games back. Brown's earned run average was the lowest on the team at 2.60, and his nine wins tied veteran Chappie McFarland for most on the team.

Mordecai and Christy Mathewson began their famous face-offs during Mordecai's rookie year. The first time they met, on July 9, they dueled through eight innings, not allowing a run. In the ninth inning the Giants got to Mordecai for three runs and beat the Cardinals 4-2.

Biographical material by Cindy Thomson - SABR Bio Project