 Brennan fought future Hall of Famer Billy Miske twice in 1919, once on June 28 in Oklahoma to a fifteen-round loss on points, and on April 28 at Cardinal Field in St. Louis to an eight-round newspaper decision draw.He lost to Miske again on June 8, 1921, at the Auditorium in St. Paul on a ten-round newspaper decision.According to the "Decatur Daily Review", Miske took five rounds, Brennan two, and three were even.