The Cubs signed Bummer to a minor-league contract Wednesday, Bob Nightengale of USA Today reports.
Bummer was released by Atlanta last week after collecting a 7.63 ERA and 1.83 WHIP across his first 19 relief appearances this season. The lefty's velocity has been tumbling in the wrong direction in recent years, but the Cubs will stick him at Triple-A Iowa and see if they're able to coax more out of the 10-year veteran.