The Athletics designated McKinney for assignment Monday, Martin Gallegos of MLB.com reports.
He'll be pushed off the 40-man roster in favor of Luis Barrera, who was also called up from Triple-A Las Vegas to take McKinney's spot on the 26-man active roster. McKinney had managed a lowly .096/.158/.173 slash line while striking out in 28.1 percent of his plate appearances through the first month of the season, so he could have a tough time earning a spot on another organization's 40-man roster. If he goes unclaimed off waivers, McKinney will be assigned to Las Vegas.