Chark (ankle) isn't participating in Thursday's practice, Dave Birkett of the Detroit Free Press reports.
After opening the week as a limited participant Wednesday, Chark was sidelined Thursday along with top wideout Amon-Ra St. Brown (ankle), who also sat out Wednesday's session. Taking a step back in the middle of the week in terms of practice activity typically isn't a promising sign, though it's conceivable Chark's absence from Thursday's session may have been maintenance-based. Whatever the case, Chark -- as well as St. Brown -- will likely need to get back on the field in some fashion Friday before the Lions provide a gauge for their chances of suiting up Sunday against the Seahawks.