The good: There was a lot of good play this past season scattered along Detroit's defensive front.

Let's start with defensive tackle Damon Harrison, who the team acquired via trade with the New York Giants at the deadline.

The returns on that investment showed up immediately on the field for the Lions. After he joined the defense Week 8, the Lions allowed the second lowest yards per rush average in the league (3.76) and the fourth fewest rushing yards (925) the rest of the season. He was exactly the kind of player head coach Matt Patricia needed to anchor the middle of his defense.

The Lions practiced in the preseason against the Giants. They not only got a close look at Harrison at the time, but also edge rusher Romeo Okwara. When he was part of New York's final cuts, the Lions saw potential and claimed him. He went on to record 7.5 sacks and force a fumble in 15 games for the Lions.

It also looks like Quinn hit on fourth-round pick Da'Shawn Hand. He's shown to be versatile and explosive, and was graded the top rookie interior defensive lineman this past season by Pro Football Focus. Detroit's veteran defensive linemen have raved about his potential.

A'Shawn Robinson also had a very good third season. He recorded 49 tackles and was very good against the run in 13 games played.

The signing of veteran Ricky Jean Francois also turned out to be a good one for Detroit, not just because of his solid play in a reserve role upfront, but also because of his knowledge of Patricia's scheme, his willingness to teach it, and his leadership.

The bad: The Lions used their franchise tag on on defensive end Ziggy Ansah.

Ansah has been held back by injuries throughout his six-year career, and that was again the case in 2018. He injured his shoulder Week 1 vs. the Jets, which forced him to sit out the next six games.

He came back and played in seven games (recording four sacks), but re-injured his shoulder Week 14 and was lost for the year.

Detroit signed nose tackle Sylvester Williams last offseason in hopes that he could be an anchor in the middle of their line. It just never panned out that way, and resulted in the Lions trading for Harrison. Williams was released when the Lions acquired Harrison.

Key stat: Harrison (2nd) and Robinson (5th) finished the season graded in the top five among interior defensive linemen against the run by Pro Football Focus. No other team in the league had two interior defenders ranked in the top 10 against the run.

Free agents: Ansah is an unrestricted free agent. It will be interesting to see what kind of market develops for him. When healthy, he's one of the game's best coming off the edge, but availability has been an issue for him throughout his career. Jean Francois is also an unrestricted free agent.

Okwara is a restricted free agent. The Lions seemed to really like how he developed in their scheme, and he should get better the more he adds muscle to his frame. He seems like a candidate to get a restricted offer, whether that's a first, second or original-round tender will be interesting to see.

Kerry Hyder Jr. is also a restricted free agent. Credit him for making a comeback this year from a devastating Achilles injury that cost him all of 2017. He has six tackles and a sack in seven games as a reserve.

Mitchell Loewen, who the team signed off waivers from New Orleans Week 17, is an exclusive rights free agent. At 6-foot-5 and 275 pounds, we'll see if the Lions can mold him into a contributor.

Draft: This draft is LOADED with defensive line talent. ESPN draft analyst Todd McShay released his first Top 32 draft prospects column and six of the top 10 were defensive linemen, led by Ohio State defensive end Nick Bosa and Alabama defensive tackle Quinnen Williams at the top two spots.

Nearly half (15) of McShay's Top 32 players available right now play defensive end or defensive tackle. If teams want to add to that unit, this is the draft to do it.

MVP: Harrison's acquisition completely changed the trajectory of the Lions' defense, not only this year, but for future seasons as well. He's under contract for another two years. He led all defensive tackles with 81 total tackles and 52 solo tackles. He's the first defensive tackle in NFL history to finish with 80-plus tackles, nine tackles for loss, 3.0 sacks and two forced fumbles.

Most improved: It was kind of a strange year for Robinson, who began the season as a healthy scratch Week 1. He went on to become one of the key components upfront alongside Harrison. Robinson finished the season graded 12th best among all NFL interior defenders by PFF. He finished 46th in that grading last season and 27th in 2016 at the conclusion of his rookie season.

The multiple defensive scheme Patricia has implemented in Detroit really seems to suit Robinson's skillset. Credit the third-year pro for busting his butt this season to become a real impact player within it.

Quotable: "I think that's a great example of an area that definitely got stronger in a direction that we wanted to and trying to build from the ball out, which is always a good way to do it," Patricia said of the defensive line after the season.

"I think those guys really learned a lot, I think they got better. I think the fundamental stuff that we talked about even going back through to training camp was things that with those guys inside especially you could really see the learning of the technique pay off as the season went on."