Defensive Tackle
The Lions have defensive tackles Danny Shelton, Da’Shawn Hand, Nick Williams, and John Penisini returning. Shelton and Williams could both be released to free up cap space. Hand’s health is a primary concern and it would be hard to rely on him being a starter.
Sixth-round rookie Penisini has played exceptionally well compared to his draft position. However, he will have to make great strides in his game to beat out potential free agents and rookies for a starting job.
Outside of Shelton, Detroit doesn’t have a defensive tackle to rely on week in and week out. They also don’t have any top-end pass rushers in this group. They need a three-down player, one who can stop the run and generate constant pressure.
Middle Linebacker
Second-year linebacker Jahlani Tavai is the only middle linebacker on the roster for next year. I’d assume most wouldn’t need a write up explaining why the position is one of Detroit’s biggest needs.
Outside Linebacker
Outside linebacker Jamie Collins is underrated and a player that most wouldn’t think is essential. Despite the direction the Lions decide to take going forward, Collins has value.
Due to his versatility and ability to do almost everything on the field, he’s great to have in a rebuild because younger players can lean on him. If you surround him with more talent in the front-seven, his play will only get better.
Depending on the defensive scheme Detroit runs on defense, they potentially need two more outside linebackers, making this a significant need for them.
Safety
I’m still a believer in safety Tracy Walker and he could excel in a different scheme. Regardless, safeties Duron Harmon and Jayron Kearse are pending free agents. Second-year safety Will Harris hasn’t shown enough to promote confidence.
The Lions might be looking for two or potentially three safeties this offseason. Kearse would be a smart option to bring back. He has the size and plays physical enough to match up with tight ends. Like Walker, Kearse could benefit from a new scheme as well.