It was easy to see coming, and this year more than ever as he navigated a litany of injuries. Aaron Glenn has left his post as Detroit Lions defensive coordinator to be the head coach of the New York Jets, which was also easy to see coming.

So Dan Campbell has to replace both of his coordinators, which he openly told reporters he expected to have to do on Monday morning. By that afternoon Ben Johnson was gone, and about 48 hours after that so is Glenn.

It’s clearly time for a fresher list of candidates to replace Glenn.

5 potential candidates to replace Aaron Glenn as Lions defensive coordinator

5. Michigan defensive coordinator Wink Martindale

With a massive hat-tip to Christian Booher of SI.com, Martindale makes a lot of sense as a candidate to replace Glenn. He favors a blitz-heavy style similar to how Glenn did/does.

Prior to this past season as Michigan’s defensive coordinator, Martindale worked exclusively in the NFL going back to 2004, including three stints as a defensive coordinator-Denver Broncos, 2010; Baltimore Ravens, 2018-2021; New York Giants, 2022-2023).

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.

2. Lions defensive assistant Jim O’Neil

O’Neil has spent the last two seasons as a defensive assistant with the Lions, with focus on working with the safeties that taps into his history as a defensive backs coach. The work done by Kerby Joseph, Brian Branch and Ifeatu Melifonwu (for his brief fully healthy stretch late in the 2023 season) stand as prominent marks on his resume.

But O’Neil also has some experience as a defensive coordinator. He was the defensive coordinator at Northwestern for two seasons before coming to the Lions, and he had stints in the role for the Cleveland Browns (2014-2015) and San Francisco 49ers (2016).

Experience and familiarity automatically puts O’Neil somewhere on the radar to replace Glenn in Detroit.

1. Lions linebackers coach Kelvin Sheppard

Sheppard is a rising star, and he would be an easy candidate to follow Glenn and be his defensive coordinator in New York. But it seems like Glenn is moving in the direction of having a more experienced defensive coordinator who has head coaching experience (namely Steve Wilks), leaving Sheppard as the easy top candidate to replace Glenn in Detroit.

Glenn talked openly about grooming Sheppard for his eventual future as a defensive coordinator

“And having Shep there with me, he’s been there from the beginning, and he knows exactly how I think – exactly,” Glenn said last month, via Ben Raven of MLive. “And that’s a guy that I’ve been actually mentoring to be in the DC role at some point.”

In light of Glenn’s looming departure (which has now of course happened), Jordan Schultz of FOX Sports noted Sheppard as a “hot name” to land a defensive coordinator role.

“If Aaron Glenn lands a head coaching job, keep an eye on #Lions LBs coach Kelvin Sheppard as a hot name for landing a defensive coordinator role.”

“Sheppard, who played eight NFL seasons, has a sterling reputation inside the Detroit building and across the league as a whole.”

Note how Schultz’s report did not get directly specific about Sheppard replacing Glenn as Lions defensive coordinator, but that he’d generally be a candidate for a defensive coordinator job. So Campbell may need to move quickly to keep Sheppard in the fold.