When the Milwaukee Brewers acquired Brad Miller, they immediately optioned him to Triple-A where he could get some work in at shortstop. Miller came up as a shortstop but has been playing first base and second base most recently for the Rays. So he needed some time to adjust to his new primary position.
With the Crew playing well, they’re not desperate for Miller to join the squad. Despite Orlando Arcia‘s struggles offensively, the Brewers are winning games and are willing to stick with Arcia because of his glove in the field.
The idea behind acquiring Miller was to help out the big league club, not Triple-A.