Mann was platooned in the outfield of the 1914 World Champion Braves; the next year he jumped to the Federal League and led that circuit with 19 triples. He headed a player revolt for better shares in the 1918 WS as a member of the pennant-winning Cubs. He batted over .300 six times, mostly as a reserve; in his three seasons with the Cardinals (1921-23), he hit .328, .347, and .371. He turned in Giant pitcher Phil Douglas for writing him a letter inviting a bribe in 1922. After his playing days, Mann formed the National Amateur Baseball Association. In 1936, he persuaded the World Olympic Committee to add baseball as an exhibition event; two American teams puzzled a throng of Germans, who formed a larger crowd than had ever attended a World Series game.