The Phillies announced earlier that third baseman-turned-outfielder Cody Asche would re-join the Phillies big league club today in time for the Phillies to take on the Colorado Rockies. Hours later, the Phillies announced the corresponding roster move that would make room for new outfielder Cody Asche.
OF Grady Sizemore has been designated for assignment to make room for @cody_smasche on the 25-man roster.
— Phillies (@Phillies) May 29, 2015
The Phillies have 10 days to decide what to do with his contract. They can trade Sizemore, assign him to AAA (which he can reject and become a free agent), or outright release Sizemore.
Because Sizemore was not outright released, they may hope to keep Sizemore at AAA for insurance. Sizemore was re-signed early in the offseason before the Phillies added outfielder Odubel Herrera. Even with Domonic Brown in the fold, the Phillies chose to keep Sizemore around. But, with Asche batting .310 at AAA and playing adequate defense, the Phillies opted to bring Asche back to the major leagues.
Speaking of Brown, there is no stated timetable as to when he would return.