One big question mark on the defense is who will replace Devon Kennard at the JACK linebacker spot.
The JACK linebacker is a unique position that not every NFL team has.
It is similar to a 3-4 outside linebacker in many ways, but head coach Matt Patricia does not always use a 3-4 scheme.
Even when deploying even fronts, the JACK still usually plays more of a stand-up defensive end role.
Second-year player Austin Bryant and rookie third-rounder Julian Okwara were expected to play a big role on the edge – and they very well still could.
However, it would appear the Lions are giving Christian Jones a fair shot as the starting JACK.
Last season, Jones was listed as an off-ball linebacker, but he saw plenty of time on the defensive line as well.
Actually, he lined up more on the edge than he did anywhere else.
Unfortunately, in terms of pass rushing, there was very little success. It wasn’t much better against the run, either.
Now, with the addition of Jamie Collins – who can also play on the edge – Jones’ WILL linebacker spot from a season ago looks to be Collins' to lose.
That's not to say that Collins or any of the other stack linebackers won't occasionally move around.
The Lions have plenty of versatile linebackers, and that flexibility is a big part of Patricia’s scheme.
Speaking of scheme, another linebacker that has some potential but isn’t a prototypical fit for the defensive philosophy is fourth-year backer Jalen Reeves-Maybin.
Looking at what Patricia likes in a linebacker, Reeves-Maybin isn’t exactly tailored for the gap-plugging system.
Maybe what he does have going for him is that he does offer a unique skill set compared to his counterparts.
Listed at 6'0 and 233 pounds, Reeves-Maybin has some nice athleticism to his game.
He can use that to his advantage in the passing game, yet his size doesn’t make it easy for him to hold his ground against bigger linemen.
His length also doesn’t make him a great fit to move down to the edge, like most of the Lions' linebackers are capable of performing.
The biggest thing Reeves-Maybin has going for him is his special teams ability.
Considering how much of an emphasis general manager Bob Quinn places on the third phase of the game, it would make sense for the Lions to create a little more of a specialized role for Reeves-Maybin on defense in order to get the best of both worlds.
All in all, the linebacker spot is a fluid situation.
It will be interesting to see how certain individuals will be deployed.