Jackson, who was sent to extended spring training Wednesday, will be shut down as he deals with a shoulder injury, the Seattle Times' Ryan Divish reports. He has apparently been playing through the injury since spring training, which helps to explain his struggles at Low-A so far this season. It is unclear how serious the injury is but his status as a top-100 prospect in dynasty leagues has not changed. Jackson should not be expected in the big leagues until around 2019, so try not to overreact to things that may slow him down a little this season.