Peguero was optioned to Triple-A Nashville on Thursday.
Peguero has pitched nearly the entire season at the big-league level and maintained a solid 2.98 ERA across 51.1 frames. However, his 4.7 BB/9 has led to an inflated 1.54 WHIP. He'll head to the minors, though he would be a candidate to return to the majors if the Brewers require depth out of the bullpen later in the month.