 Mosberg was in a rough and close twelve-round fight on April 22, 1922, with Mickey Donley at the Clermont Avenue Rink in Brooklyn.Mossberg knocked Donley to the canvas in the opening round, but the majority of the bout was even, though the boxers mixed it up throughout.On June 26, 1922, Mosberg was knocked out a few seconds into the first round by southpaw Eddie Fitzsimmons in an important twelve-round, semi-final match before a huge crowd of 20,000 at New York's Bronx Velodrome.