Alfred S. Mannassau (1866 – October 13, 1933) was a professional baseball umpire, manager and player.
[2] In 1898, Sporting Life characterized Mannassau's umpiring work in the Western League as "grossly incompetent", saying that Mannassau had "feigned sickness and left the field" that day in response to persistent protests from fans.
By midseason, J. Earle Wagner of the Washington team publicly criticized the umpiring of Mannassau and his partner.
Wagner expressed a desire to return to the one-man umpiring system the following year.
Mannassau enraged Duffy, who would end up in the Hall of Fame, with a fair ball call that went against Milwaukee and resulted in the team's defeat.