Gilchrist signed with the Lions on Thursday, Dave Birkett of the Detroit Free Press reports.
The Lions dealt safety Quandre Diggs to the Seahawks this week, leaving a need for depth in an already banged-up secondary. In steps Gilchrist, who logged 58 combined tackles and three interceptions across 16 games with Oakland in 2018. The eight-year veteran is immediately a candidate to see snaps in the secondary.