He started his professional baseball career in 1884 with Terre Haute of the Northwestern League.

[1] Seward joined the American Association's Philadelphia Athletics in 1887.

In 1888, Seward went 35–19 with a 2.01 ERA, and he led the AA with 272 strikeouts and 6 shutouts.

[2] On July 26, he threw a no-hitter against the Cincinnati Red Stockings.

[2] After his playing career ended, Seward was an NL umpire in 1893.