The Brewers acquired Ornelas from the Athletics on Saturday in exchange for cash considerations.
Ornelas was pushed off the Athletics' 40-man roster Monday, but he'll reclaim a spot upon moving to Milwaukee. He'll report directly to the big club to help shore up the Brewers' infield depth as they navigate injuries to Brice Turang (knee) and Cooper Pratt (hamstring). Ji Hwan Bae was designated for assignment in a corresponding move.