The Cincinnati Reds' new owner continues to put his stamp on the team.
FOXSports.com has learned that Bob Castellini has fired general manager Dan O'Brien.
An announcement is set for Monday afternoon.
Friday, in his first day running baseball's oldest professional franchise, Castellini, a produce magnate, reorganized the front office and promised fans a championship.
Castellini's first move was to change the front office's structure. Chief operating officer John Allen will stay but will focus on the business side of the ballclub. O'Brien's replacement will run the baseball side, reporting directly to Castellini.