Zych (shoulder) had his rehab assignment transferred to Double-A Jackson on Monday, Bob Dutton of the Tacoma News Tribune reports.
Zych had been rehabbing in the Arizona Rookie League, but he'll now progress to Double-A as he nears a return to the big league club. The Mariners have not offered much in the way of a firm return timetable, but Zych looks to be on track to be back with Seattle sometime later this month.