Peguero was placed on the 15-day injured list Wednesday, retroactive to Sept. 17, with a right elbow effusion, Sophia Minnaert of Bally Sports Wisconsin reports.
It's unclear when the injury first surfaced for Peguero, but he hasn't pitched since he delivered 1.1 scoreless frames Saturday against Washington. The right-hander will miss the rest of the regular season but will be eligible to return in the playoffs, which the Brewers are undoubtedly hoping for given his 3.38 ERA and 21 holds in 59 outings this year.