The edge gets most of the attention and most of the money, but the interior of the defensive line has become just as important over the past few seasons. With an increased emphasis on quick-strike passing and spread formations that are used to run the ball up the middle, 4-3 defensive tackles and 3-4 defensive ends and nose tackles have never been more important. A game-wrecker at any of those positions can change the course of a possession and swing a game on his own. 

This year's free-agent crop at those positions is strong, and also deep. It doesn't have outright stars like the edge crop, but there's a whole lot of talent here. 

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Let's break it all down. 

Every down difference-makers

Grady Jarrett, Ndamukong Suh, Sheldon Richardson, Muhammad Wilkerson

Jarrett is the crown jewel of the interior defensive line class. He'll turn 26 years old in late April and has been getting better and better with each passing season. In 2018 he recorded 52 tackles (eight for loss), six sacks, 16 quarterback hits, 36 hurries, and 30 run stops, per Pro Football Focus. He seems extraordinarily likely to be franchise-tagged by the Falcons if they can't come to a long-term agreement by the deadline (CBS Sports NFL Insider Jason La Canfora put him in the "virtually certain" to be tagged camp on Monday), but if he is able to hit the open market, he could become one of the highest-paid defensive tackles in the league.

Suh is coming off a very good but not necessarily great season playing next to Aaron Donald and Michael Brockers in LA. A short-term, mid-to-high-tier dollar deal seems the most likely result for a player of his age and caliber. He's still a high-level player at 32 years old, capable of single-handedly wrecking a game like he did during the playoffs against Dallas and New Orleans. He's a very good pass rusher and run defender, and if the Rams decide the price is too high, he could really help somebody else. 

Both in their late-20s, Richardson and Wilkerson are at similar stages of their respective careers. However, the former Jets defensive linemen are coming off polar opposite seasons. Richardson played very well for the Minnesota defense and likely made himself some money coming off the prove-it deal he signed last offseason while Wilkerson lasted only a few games in Green Bay before suffering a season-ending injury. Richardson is likely the better player (and less of a headache) at this point, but both players have the potential to make an impact on all three downs and could prove extremely valuable in the right situation. 

Upside plays

Henry Anderson, Malcom Brown, Tyeler Davison, Mario Edwards, Johnathan Hankins, David Irving, Jordan Phillips, Darius Philon

A former third-round pick of the Colts, Anderson is coming off the best year of his career, having racked up seven sacks, seven tackles for loss, 16 QB hits, and 25 run stops with the Jets in his first season in New York. His strength is the versatility that allows him to play all over the line, and at 27 he should still have plenty of high-level years left in him. 

Brown is a terrific run defender who has played very well in a very demanding New England defensive scheme, but he is almost a complete non-entity as a pass rusher. He did not have a single sack last season and has recorded just 16 quarterback hits in his four-year career. Still, he just turned 25 years old earlier this month and he's shown himself to be extremely effective on early downs. The same applies to Davison, except he's two years older and has done it for New Orleans instead of New England.

Edwards is a former early second-round draft pick but has only been varyingly effective in four seasons with the Raiders and Giants. He doesn't turn 25 until early April, though, so he can be an intriguing "second draft" prospect for someone seeking cheap help along the defensive line. The same applies to Phillips, who was waived after three-plus seasons in Miami and was moderately effective for the Bills last season. 

Hankins has always been one of the more underrated players in football. He's been effective at every stop, whether with the Giants or Colts or Raiders. He'll turn 27 in March but he's got 34 hits and 27 tackles for loss in six seasons as largely a part-time player. Philon's a similar player, but he's two years younger and has shown more pass-rush ability and so can be on the field more often. If the Chargers decide they don't want to pay another player along the defensive front, maybe somebody else can snag him. 

Irving has fallen out of favor in Dallas due to repeated issues with the substance-abuse policy and some personal issues off the field. He has flashed special talent at times and doesn't even turn 26 until training camp, so if some team can get a handle on his various issues he could be a very good upside play. 

Run-stopping specialists

Danny Shelton, Bennie Logan, Haloti Ngata, Al Woods, Clinton McDonald, Domata Peko, Brandon Mebane

Shelton is a bit younger than everybody else on this list and likely has the highest single-season and long-term upside among them at this point, but they are all remarkably similar players. Shelton will likely command a longer-term contract but anybody expecting him to suddenly display pass-rushing prowess is likely expecting too much. If you need a two-down run-stuffer one one-year deal, any one of the older veterans here should fit the bill. Among the vets, Peko is likely playing at the highest level at this point, but Mebane has been a quality piece for the Chargers, Woods has played well in several stops, and McDonald, Logan, and Ngata all have their merits as well. 

Veteran contributors

Margus Hunt, Christian Covington, Brent Urban, Kerry Wynn, Allen Bailey, Ricky Jean-Francois, Tyson Alualu, Zach Kerr, Kyle Love, Earl Mitchell

In much the same as there was on the edge, there is a strong, deep group of solid veterans available on the defensive interior. This is a 10-player list right here and there are more where they came from. All of these guys have been productive throughout their careers, and they all were effective to some degree in 2018. They're not necessarily elite run-stoppers like the group of guys above, but they've also got a bit more in the pass-rush department than that group does. If you just need some bodies and some depth, you could do a whole lot worse than signing any one of these guys. And if you're lucky, they'll provide a lot more than mere depth.