In the age of re-invention and offensive expansion, the NFL offers its defense for Super Bowl 50 and the Eagles work on how to get that side of the football to championship-level standards.

Both Carolina and Denver reached the Super Bowl in part because of the strength of its defenses. Carolina, we saw during the 2015 season, has a dominating front, lightning-quick linebackers and a secondary that contributed to the Panthers' league-leading total of 39 takeaways, a vitally important statistic in the league. The top five teams in takeaways -- Carolina, Kansas City, Cincinnati, Arizona and New England -- reached the postseason. Denver's defense, meanwhile, has been nothing short of awesome for most of the year, particularly in the postseason. Four of its starters -- cornerbacks Chris Harris Jr. and Aqib Talib, and linebackers Von Miller and DeMarcus Ware -- were voted into the Pro Bowl and all have had dominating playoffs.

So while we've talked about how the Eagles stack up in the 4-3 front it's also worth looking at the back end and the pieces that coaches Cory Undlin and Tim Hauck have at their disposal.

The cornerback spots have veteran Byron Maxwell and second-year man Eric Rowe back as the on-paper starters. Certainly, the Eagles need more from Maxwell in his second year here than he produced in 2015 and perhaps his level of comfort will be enhanced in the new scheme, which could feature more zone concepts than man-to-man coverage responsibilities. We'll see on that. Defensive coordinator Jim Schwartz wants to change his fronts and his coverages and his rush-the-passer packages. He wants multiple everything. He was versatile plans from one week to the next. 

Anyway, Maxwell needs to be better. More competitive. More fiery and, simply, more of the tenacious cornerback the Eagles expected when they signed him to a free agent deal.

Rowe made humungous strides as a rookie. He took his lumps in the preseason, had a couple of good moments early in the regular season and then was thrown into the starting lineup in the final five games and got better and better and better. He has a chance to be really good, and his improvement is a testament to Undlin's teachings and the amount of work Rowe put into his craft. This is a big offseason for Rowe, who has to get a lot better, but he has a great upside.

What about the rest of the picture at cornerback? Nolan Carroll and E.J. Biggers are scheduled to become unrestricted free agents on March 9, so their futures are uncertain. Youngsters like Jaylen Watkins, Denzel Rice, JaCorey Shepherd (coming off an ACL injury) and Randall Evans will have chances to push into the rotation and earn playing time. There is promise, yes, but there is also uncertainty.

Same as the safety spots. The Eagles are glad to have Malcolm Jenkins patrolling the deep secondary and his leadership and ability to play in coverage and support the run defense really help in Schwartz's scheme. Jenkins enjoyed his Pro Bowl experience and hopefully he will have the chance to return, because the defense is going to funnel the ball into the middle of the field and Jenkins will be around the football a lot in 2016.

Who lines up next to Jenkins, though? It's a big question. Walter Thurmond is scheduled to be an unrestricted free agent after his solid 2015 campaign. He stayed healthy, he was productive and he fit into what Bill Davis asked. What is Thurmond's next step? Does he stay or does he go? And if he goes, who replaces him?

Chris Maragos and Ed Reynolds saw some snaps at safety and Reynolds, in particular, got his hands on the football at opportune times. Can either become a starting player? Is Jerome Couplin ready to take his next step and contribute?

The overall picture of the secondary is part promise, part question. The Eagles have some areas to address in the back of the defense to complement what appears to be a pretty well-stocked group up front.

More news, notes and little bit of this and that ...

• No shock that former Eagles wide receiver (albeit for such a brief time) Terrell Owens did not reach the Pro Football Hall of Fame in voting on Saturday. T.O. made the final field of 15 and was eliminated on the vote down to 10 candidates. He will be a strong candidate in 2017 when both Brian Dawkins and Donovan McNabb are eligible. Is Dawkins a first-ballot Hall of Famer? Geez, if there ever was one, Dawkins would be the guy, right? McNabb, as much as he was successful here, is going to have a tough time making it to the Pro Football Hall of Fame. 

• I hear a lot from Eagles fans about adding to the wide receiver position, and I'm sure that when it's all said and done and the Eagles configure their roster they will have some competition at wide receiver. But understand that they are really high on Ronald Darby and they think Nelson Agholor is going to take a huge step forward in Year 2 and that Josh Huff has some characteristics that are really impressive but must be made more consistent. There are some pieces to work with here. And, once again, the Super Bowl teams show you that you don't need a "superstar" wide receiver to win it all. I just don't see the Eagles being players in, for example, the high-stakes world of free agency. There will be some players out there, but the pickings are going to be slim for the "top end" wide receiver. And this team has other, more glaring needs.

• Will the Eagles add a young quarterback in the offseason, in the draft or in free agency? It's obviously a huge question, so remember that both Sam Bradford and Thad Lewis are scheduled to be unrestricted free agents. It makes sense that, at some point, the Eagles would bring at least one more quarterback on board. Of course, it all depends on what happens with Bradford and, to an extent, with Lewis. That is all part of head coach Doug Pederson and his coaching staff's "evaluation" that is ongoing. It's really hard to get a feel for what's going to happen at the game's most important position for the Eagles, but we know this: Free agency starts on March 9. This roster is going to take shape in a very short period of time.