The Athletics designated McFarland for assignment on Friday.
The left-hander spent most of May on the IL due to a groin injury before being activated in early June, and he'll lose his place on the 26-man and 40-man rosters after giving up six runs in nine outings after being reinstated. McFarland has a decent track record in the majors and will have the option to elect free agency if he clears waivers.