Mills allowed five runs (two earned) on four hits and one walk over one inning in Saturday's 12-5 loss to the Padres.
Mills made his Cincinnati debut after his contract was selected from Triple-A Louisville last Tuesday. A one-time starter and long reliever, most recently with the Cubs, Mills was brought in as a reliever with potential to be a spot starter for a staff that currently has four healthy arms. He needed 40 pitches Saturday, which may preclude him from being used as a traditional starter for Tuesday's game in Washington, the next time the Reds need a fifth starter.