Farrell was recalled from Triple-A Iowa on Friday, Jesse Rogers of ESPN.com reports.
Farrell has acted as a starter for the I-Cubs this season, but he'll head to the Cubs' bullpen for now to replace long reliever Eddie Butler (groin), who was placed on the disabled list in a corresponding move. The 26-year-old Farrell likely won't be used in high-leverage innings given his 5.91 ERA in two Triple-A starts.