The Brewers selected Monasterio's contract from Triple-A Nashville on Saturday.
The 25-year-old will get his first taste of the majors, replacing Willy Adames (concussion) on the active roster, after spending nearly a decade in the minor leagues between four different organizations. Monasterio has displayed a discerning eye at the plate with more walks (32) than strikeouts (29) so far this season, and he can run a little as evidenced by his 11 steals through 42 games. However, it remains to be seen exactly what his role will be with the big club.