The club made the announcement after its 4-3 loss to Philadelphia.
The 28-year-old Miller batted .256 with five home runs and 21 RBIs this season. His best year came in 2016, when he batted .243 with 30 homers and 81 RBIs.
Miller was optioned to Triple-A Colorado Springs, though his time there could be short. Milwaukee is beat up and struggling in the middle of their infield. Shortstops Eric Sogard and Orlando Arcia are batting .114 and .207, respectively. Potential replacements — Tyler Saladino and Mauricio Dubon — are currently on the disabled list. The move for Miller gives general manager David Stearns more options.
Choi, who joined the team as a free agent last offseason, played in 12 games for Milwaukee. He batted .233 with two home runs, including a game-changing grand slam against Philadelphia this weekend. The return of Eric Thames from the disabled list, which is expected Monday, gives the Brewers remarkable depth at first base and made Choi expendable.
Milwaukee opens a series with the Chicago Cubs on Monday night at Miller Park.