The Cubs selected Blach's contract from Triple-A Iowa on Sunday.
Blach joined the organization on a minor-league deal in mid-April and has gotten into five games (three starts) for Iowa, posting a 5.23 ERA, 1.68 WHIP and 14:7 K:BB over 20.2 innings. He'll likely work in long relief out of the bullpen with the big-league club. Reliever Hunter Harvey (triceps) was moved to the 60-day IL to make room for Blach, while Javier Assad was optioned to Triple-A.