[Editor's note: This is the second installment in Senior Analyst Mike Renner's “Teaching Tape” article series, which takes a look at the best positional units across the NFL. Last week, Renner broke down the league-leading play of the Dallas Cowboys' offensive line.]

Earlier this offseason, every analyst at PFF was asked to put together their list for the Top 101 players of 2015, and the choice for No. 1 was easy to me. In Week 12 of last season, I did the first-run analysis for the Carolina Panthers' demolition of the Dallas Cowboys, and in four years of working at PFF, I’ve never seen a more impressive performance from a linebacker than Luke Kuechly’s that day. Never mind that he missed three games over the course of the year, any player capable of doing that had to be No. 1 on the list.

In the end, I succumbed to well-reasoned arguments about other players’ bodies of work, and Kuechly ended up third on PFF’s official list, but at their peak, no linebacking corps changed the way opposing offenses had to play more than the Panthers, and that’s why they are the next installment in our look around the league’s most impressive units.

When analyzing the Panthers linebacking duo of Luke Kuechly and Thomas Davis, the first thing I noticed that makes them so special is their difficulty of assignment; they have the hardest job of any linebacking corps in the league. It starts with the fact that the Panthers played nickel defense (four down linemen, two linebackers, and five defensive backs) far more than any other team in the league last season. 73.6 percent of the Panthers' defensive snaps a year ago came in nickel personnel, while the Steelers were the next closest at 66.2 percent. Most teams wouldn’t dare match up against a two-tight end set with only two linebackers, but the Panthers did it over five times a game, on average. This gives them the unenviable task of stopping the run with a much lighter box than opposing offenses. The results, though, speak for themselves.

While their run defense was superb as a whole, what makes them truly special is their prowess in coverage. One of the reasons the Panthers were in nickel so much is because, even against four- and five-WR sets, they never went into dime (six defensive backs). That means that defensive coordinator Sean McDermott trusted Thomas Davis and Kuechly so much that he felt comfortable with them having to cover wide receivers if need be.

Outside of the personnel aspect, the Panthers also asked a ton of their linebackers schematically. Carolina played quarters coverage (cover four) on 26.7 percent of their snaps last season, again the highest rate of any team in the league. Quarters asks their linebackers to cover a ton of ground. Below is an outline of each defenders' basic zones in a quarters defense.

That’s obviously a very simplified version of a complicated defense that varies based on route concepts, but the key is that three underneath defenders are asked to cover all 53-and-one-third horizontal yards of the field. Now, there are a handful of variations on quarters, and the LBs' responsibilities can differ greatly based on the formations, but it’s still a defense that requires those underneath defenders to be extremely disciplined in their assignments and route recognition, or else they’ll leave large holes in those underneath zones. And when it comes to reading route combinations, no one does it quite like the Carolina pair.

Kuechly and Davis are relied upon so much for the Panthers' defensive identity, and own the first- and fifth-highest coverage grades, respectively, each of the past two seasons for LBs—it's easy to see why they should be recognized as the top linebacking duo in the NFL. No one can match Kuechly’s instincts, while few have the fluid athleticism to match Davis. With all the losses in the Carolina secondary, don’t be surprised if they ask even more out of the pair in 2016—and be even less surprised when they deliver.

[More: See Mike Renner's article from last week breaking down the Cowboys' NFL-best offensive line.]