4. Jaguars defensive coordinator (for now) Ryan Nielsen
As the Jaguars continue their search for a new head coach, Nielsen sits in limbo and it's unlikely he'll be brought back for a second season as the defensive coordinator by the new head coach. To say nothing of the dismal results Jacksonville's defense had this season.
That said, the Atlanta Falcons had a top-10 passing defense and a top-12 scoring defense in 2023 with Nielsen running the show and it not for the coaching change there he probably would have been retained. He also served as co-defensive coordinator with the New Orleans Saints in 2022.
And that's where Nielsen surfaces as a possible candidate to replace Glenn in Detroit. He overlapped with Campbell (and Glenn) for four seasons in New Orleans (2017-2020) as the defensive line coach. Lions fans surely won't love the idea of Nielsen on the surface, but the situation in Jacksonville this past season shouldn't sully him that much.
3. Lions defensive backs coach Deshea Townsend
Townsend interviewed with the San Francisco 49ers for their defensive coordinator job earlier this month, which served as proof of his candidacy for a step up the coaching ranks. The improvement Lions cornerback Terrion Arnold showed over the course of his rookie season, and the work Carlton Davis and Amik Robertson did before their injuries, was notable as the Lions were far tougher to go against in the passing game during his first season on the coaching staff.
Townsend got right into coaching after 13 seasons (1998-2010) as an NFL cornerback, and he has experience coaching defensive backs at the college and pro levels. Glenn made the jump from defensive backs coach to defensive coordinator when he followed Campbell to Detroit, and Townsend could do the same now to replace Glenn.