The offense certainly continued to struggle on Sunday against Seattle. Similar themes continue to pop up that we discussed last week in our recap of the loss to New England. This week though, I really want to focus on a defensive effort that featured big plays up front and on the back end, with complementary football being played from start to finish.

For four straight games now, the Eagles have allowed 17 points or fewer on defense, the first time they've done that since 2009.

The Eagles racked up six sacks against Russell Wilson (the most for him this season). A useful tool for them in their pressure package was what is commonly referred to as the diamond front. It's a popular look that is prevalent throughout the league. The easy way to spot it? Look for when the defense has five players spread out along the line of scrimmage. Here's why the diamond front is so effective, and why teams all over the league use it.

ALL OF THE VIDEO CLIPS FEATURE AUDIO ANALYSIS FROM FRAN DUFFY

There are two coaching points for teams that utilize the diamond front.

1. By occupying an offensive lineman (the left guard in this case), you force the offense to use one of their best blockers to try and block someone who may not even be rushing.

2. With that lineman occupied, you've now pretty much guaranteed that all of your defensive linemen are getting blocked one-on-one. Unless the offense is willing to surrender an eligible receiver to help in protection, the rest of the offensive linemen are now left on islands. In the shot above, you can see how this benefits the Eagles, as defensive tackle Fletcher Cox explodes into the backfield to create a sack for defensive end Josh Sweat running off the corner.

The Eagles ran this diamond front with linebacker Nigel Bradham on top of the left guard on eight different occasions on Sunday, and all of them were on second- or third-and-long. Almost every time, Bradham dropped out into some sort of coverage. After taking a step or two toward the line at the snap, just to keep the attention of guard Mike Iupati, Bradham would play man-to-man on a running back, spy Russell Wilson, or drop into short zone coverage. By that point, however, his job was done. The lineman was occupied and his teammates got into the backfield to wreak havoc.

Late in the game, the Seahawks had enough. It was third-and-long, and you can see Iupati and Wilson communicating before the snap. They were sliding the protection toward the heavy part of the formation, meaning that Iupati would not be blocking Bradham. It had to be frustrating for him. Every time he would go to block him, he would drop out. Well, the Eagles had a plan for this, because on this play they decided to blitz Bradham. The running back, who was responsible for him in protection, correctly picks him up. The problem is that safety Malcolm Jenkins, who was assigned the running back in man coverage, takes off for Wilson. He does so because he sees that the back is staying in to pass protect. This is called a "green dog" blitz. Jenkins recognizes quickly that the back is staying in, replaces Bradham as a blitzer, and gets the numbers back in the defense's favor.

It should also be noted that Brandon Graham and Vinny Curry combine for a picture-perfect T-E stunt on this play, with Graham sneaking inside to get home clean as well. Graham teamed up with Jenkins to bring Wilson to the ground.

This wasn't the only sack for Jenkins on the day though, as he was a very active participant in containing and pressuring Wilson.

Whether it was as a "spy" or whether he was executing a perfect "green dog," Jenkins was constantly around Wilson, shadowing him from sideline to sideline up and down the field. He was a big part of the game plan and really helped the star quarterback feel uncomfortable throughout the course of the day.

The spike in the play of the secondary has really taken a jump with the return of players like Jalen Mills, Ronald Darby, and Avonte Maddox to the lineup. There has been a lot more press man-to-man coverage (Jenkins can't green dog like that in zone coverage) and the team has performed extremely well.

In the month of November, the Eagles lead the entire NFL in allowing opposing quarterbacks to complete just 53.2 percent of pass attempts. They've allowed fewer than 225 passing yards in five straight games.

That success comes from playing a lot of man coverage on third down, but on Sunday, I thought the Eagles did a really good job of mixing things up on the back end, leaning on a combination of both man and zone coverage looks. A coverage that they had a good amount of success with was Cover 2 Invert.

To explain Cover 2 Invert in the simplest way possible, your corners and safeties flip responsibilities. Instead of the safeties playing deep and splitting the field, it's the cornerbacks, as the safeties drop down to play underneath. One of those safeties is playing in the intermediate area of the middle of the field to take away crossing routes that have become so prevalent in today's game. This is a coverage that can be well disguised, and while it does have its weaknesses (as does every form of coverage), it takes away a lot as well.

The Eagles used this coverage well, and one of the beneficiaries was Rodney McLeod, who in the clip above netted a pick and a sack. McLeod is one of just four safeties in the NFL to post at least 13 interceptions and nine forced fumbles since 2013 (a list that also includes Jenkins).

The defense is playing extremely well right now. The team will need to continue that play down the stretch, where wins will become more and more important as the Eagles make a push for the playoffs.

Fran Duffy is the producer of the Emmy-nominatedEagles Game Planshow which can be seen every gameday during the season on NBC10 in Philadelphia. He is also the host of two Eagles-related podcasts,Eagle Eye in the Sky, which examines the team from an X's and O's angle each and every week as well as theJourney to the Draft podcast, which covers college football and the NFL Draft all year round. Fran also authors the Eagle Eye in the Sky column, which runs four times a week during the football season to serve as a recap for the previous game and to preview the upcoming matchup. Prior to joining the Eagles in 2011, Duffy was the head video coordinator for the Temple University football team under former head coach Al Golden. In that role, he spent thousands of hours shooting, logging, and assisting with the breakdown of the All-22 film from the team's games, practices, and opponents.