The Cubs placed Brewer on the 15-day injured list Friday with a lower-back injury, Taylor McGregor of Marquee Sports Network reports.
It's not clear when Brewer's back began bothering him, but his last appearance came Sunday in Pittsburgh. He's been an effective middle reliever for the Cubs this season, collecting a 3.09 ERA and 12:4 K:BB over 11.2 frames. Porter Hodge will take his spot in the bullpen.