On September 25, 1906, Armour was assaulted with blows to the face by Washington catcher Jack Warner under the grandstand in Detroit after a game between Detroit and Washington. Warner had played for the Tigers in 1905 and 1906 but was sold to Washington in August 1906. Warner stated that Armour had "branded him falsely as a disturber," and Armour blamed the failure of the 1906 Detroit team to Warner. After the season ended, team owner Frank Navin alleged that Armour had been "too lenient with the players."