The book has yet to be completed on the 2013 Philadelphia Eagles, but what a memorable story it has been thus far.

Think about some of the moments and games from this season that will last in Eagles lore for a long, long time. In the opening game against Washington, fans witnessed an offensive explosion unlike any other in the first half. Nick Foles tied an NFL record with seven (SEVEN) touchdown passes against Oakland. Sunday is another addition to the list, as everyone will always remember where they were for the Snow Bowl of 2013 against the Detroit Lions. Let's take a look at the game tape to see what went right for Chip Kelly's team on Sunday.

The elements obviously played a huge part in this game and its legacy. But who would've ever thought that a 33-yard catch by Lions wide receiver Calvin Johnson would be one of the biggest plays in the Eagles’ favor? When cornerback Cary Williams was beat on Johnson's long catch early in the game on Sunday, he made sure to let his coach know exactly how that same idea would work in his offense's favor. How did Chip Kelly respond? Let's take a look at a play late in the third quarter, and one of the turning points of this game …

It's first-and-10 and the Eagles run one of their more common passing concepts. To quickly summarize, there are two vertical routes on the outside (DeSean Jackson and Riley Cooper), a route down the seam (Zach Ertz) and two players in the flats. A spread concept like this is used to make the defense defend the entire field.

At the snap of the ball, Foles is looking to the right side of the field. Last week in my Lions preview, I wrote about the safety's ability to read the quarterback's eyes. Foles plays to that trait right now, moving the safety (Glover Quin) to that side.

Quin's eyes deceive him on this play, as his post-snap movement creates space for Cooper to run down the middle of the field, away from the cornerback. This was Williams' advice to Chip Kelly; defensive backs are having a hard time getting their footing, and they can be beat on deeper routes, especially post and corner routes.

Foles lets go of the football, and what ensues is possibly one of the single greatest catches I've ever seen. I have to imagine this was one of (if not the) hardest catches in Riley Cooper's career. Watch him here tracking the ball over his shoulder.

Two steps later, Cooper takes his eyes off the ball. Keep in mind, he is in the midst of a 40-yard sprint into the wind and snow.

Cooper looks back over his shoulder and, straight out of the Willie Mays highlight reel, looks it in. For Cooper to have the body control and eye discipline to take his eyes off the ball, completely reset and look it in at high speed through the elements is amazing to me. One of the best plays of the season by far.

Cary Williams' advice worked out for Kelly and the Eagles offense. On the very next play, Foles hit DeSean Jackson in the back of the end zone for a 19-yard touchdown. Kelly talked on Monday about how the passing game helped to open up the running game. Cooper's long catch helped turn the tide in the Eagles' favor, as a running game that had worked with moderate success early on started to hit for big gains. Let's take a look …

It's the second play of the fourth quarter, and the Eagles are down 14-6. This will be a simple inside zone run play to the left.

As you will almost always see on an inside zone, there are a pair of double teams inside. Guard Evan Mathis and center Jason Kelce work against defensive tackle Nick Fairley and linebacker DeAndre Levy. To their right, you have guard Todd Herremans and tackle Lane Johnson work against defensive tackle Ndamukong Suh and linebacker Stephen Tulloch. On the backside of the play, you have tight end Zach Ertz blocking defensive end Israel Idonije. Mathis and Kelce do a great job on their combo block, and get Fairley off-balance while getting Levy sealed off. Meanwhile, Johnson gets a pancake block on Tulloch, putting the veteran linebacker on his back.

Now it's time for McCoy to put on a show, as he leaps over safety Louis Delmas. McCoy talked after the game about defenders consistently looking to cut his legs out from under him, and he hurdled potential tacklers on more than one occasion on Sunday.

After hurdling Delmas, McCoy lands and stiff-arms cornerback Rashean Mathis. McCoy uses his arm as a weapon, keeping Mathis off of him and takes the ball 40 yards for his first touchdown of the game on a spectacular play that had a number of moving parts.

Now down by two points, the Eagles decide to go for the two-point conversion. What do they call? Old reliable, inside zone. This time (as you can see blurring by to the bottom right of the shot), they bring DeSean Jackson in motion before the snap. If Foles doesn't hand it off to Bryce Brown here, Jackson will be an option to pitch it to on the outside, but that won't be needed ...

Look at the movement Kelce and Herremans get on Suh and Fairley inside. Herremans comes off the ball with great pad level and shocks Suh at the line of scrimmage. Kelce, matched up on Fairley, does a great job sealing off the former first-round pick and creating a lane for Brown to run through. Tie ball game.

Let's go to the third play of the next series. It's second-and-4, and what do we get? You guessed it. Inside zone.

Just like McCoy's previous run in this breakdown, you've got a double team in Mathis and Kelce against Fairley, another one in Herremans and Johnson vs. Suh and the tight end (this time Brent Celek) taking care of the backside defensive end.

At the snap of the ball, you can see middle linebacker Stephen Tulloch's eyes right on the "mesh point" (the point of contact between the quarterback and running back where the handoff takes place). You can also see that, with Herremans and Johnson still on Suh, he's got the lane to get an open shot at McCoy if he reads this play correctly and attacks downhill. But watch what happens next ...

McCoy has the football, but watch Nick Foles carry out the fake. By sprinting to the outside, he causes Tulloch to hesitate for a split second. That split second costs him dearly, as McCoy blows through the hole and past the linebacker to the second level. Chip Kelly puts emphasis on his quarterbacks to carry out their ball fakes. Plays like this show you why. Again, this may or may not have been an actual read for Foles, this may have been run the whole way. That's not the point. He carries the fake out as if it was a read, and that is what causes the hesitation by the linebacker.

McCoy gets out to the second level and gets a huge block from receiver Jason Avant. Kelly talked on Monday afternoon about the play, saying Avant was on the sideline beforehand telling the coach to "run the ball to his side." Not only did Avant get his man on the ground, but he blocked him into the safety, Delmas, and took him out of the play as well. It was one cut, and McCoy had nothing but white in front of him, as he ran for a 57-yard touchdown.

Let's take a look at a similar play with a similar result. This was the dagger in the Lions' chances at a victory, running back Chris Polk's 38-yard touchdown run. This one came off a zone run as well, but it wasn't straight inside zone, but instead a "split zone" run.

It's first-and-10, and the Eagles come out in 12 personnel, with one back (Polk) and two tight ends to the right of the formation (Celek and James Casey). Casey saw a lot of action on Sunday, and was used as a blocker on a number of instances on this exact play, and it was this one that was the big hitter.

Ironically, this play was analyzed in the Lions preview last week. This is the basic "inside zone" rules along the offensive line. What makes this a "split zone" run is the action of the tight end whamming back to take care of the backside overhang defender, in this case that will be Delmas, who is coming on a blitz.

At the snap, Casey is coming across the formation to take on Delmas. You have a double team inside on Suh (Mathis and Kelce once again erase him from the play). The gap is there for Polk to hit on this run between Peters and Mathis.

The Lions have watched the Eagles on tape all year long. They know that the threat of the quarterback run is there. At this stage of the game, you have to defend all of the options. On this play, the Lions are expecting read option. Linebacker DeAndre Levy has the dive (Polk) and safety Glover Quin has the quarterback. That's where his eyes are through the mesh point.

On the white board, the Lions have this play defended. Levy is one-on-one with Polk in the hole and is in position to make the tackle. Polk has other ideas, however, as he runs through the tackle attempt by the playmaking linebacker and is off to the races. With Quin in the box to defend the quarterback run, there's no safety in the middle of the field and Polk scampers untouched for a 38-yard touchdown to put the game out of reach for Detroit. You can game plan all you want as a coach and have the schemes perfectly orchestrated, but the game still boils down to players making plays, and if the linebacker or safety can't make a tackle in space against this offense, the numbers favor the Eagles. This play was an example of just that.

After a turnover on downs, the Eagles get the ball back and have a chance to ice the game. It's fourth-and-12, and the offensive call is, once again, inside zone.

The Eagles are in 12 personnel with two tight ends on the field, so instead of just two double teams up front, you now have three.

At the mesh point, you can see, from left to right, Ertz and Peters blocking Devin Taylor, Mathis and Kelce working on Fairley and Herremans and Johnson working on Suh. Celek is blocking the backside defensive end. This looks like inside zone all the way.

This time, however, Foles pulls the ball and Celek releases for a quick pop pass. Foles said on Sunday that he and Celek were the only ones on the field who knew that the pop pass would even be in play. Chip Kelly said on Monday that if the pass was there that would be the first option, with the handoff to Polk being the second option. The Lions defense completely sold out on the run, and Foles throws a beautiful touch pass over three defenders. He hits Celek for a 27-yard gain, Celek slides down before reaching the end zone (a smart, veteran move) and the game is over. Eagles win.

THE DEFENSE HEATED UP IN THE SNOW

Week 14 brought another stellar effort from a defensive unit that has been playing lights out over the last two months. One area where they really stood out, especially given the conditions, was against the run. Consider the success the Eagles had on the ground against Detroit. The offense ran for 299 yards, their most since the Pickle Juice game against Dallas back in 2000. They averaged 6.5 yards per carry, and scored four times on the ground, and they did it against a team that hadn't allowed a rushing touchdown since Week 4 and was the third-best run defense in the NFL allowing just 82.7 yards per game. You would imagine that Detroit, in the same elements, would be able to produce similar numbers on the ground.

Not so fast.

Detroit called 30 running plays on Sunday. Five of them went for more than 5 yards, and the longest went for 8. Of the 30 called running plays, 15 of them went for 2 yards or fewer. Going into the game, Joique Bell averaged 4.1 yards per carry. He mustered just 3.0 per rush on Sunday. The Eagles offensive and defensive lines were the difference against the Lions, and I want to show you the evidence of it from the defensive side of the football now.

It's third-and-6, and the Eagles come out in one of their nickel subpackages, with Connor Barwin, Vinny Curry, Clifton Geathers and Brandon Graham lined up on the line of scrimmage (from left to right).

Look at the penetration Geathers gets off the snap (left circle), bench pressing Detroit's center into the backfield and causing Bell to stop in his tracks. Graham does a great job setting the edge on this play as well, keeping everything inside (right circle).

Bell attempts to cut it back and runs into the waiting arms of Barwin, who holds him up long enough to help force the ball out with Graham's help. The ball comes loose and the Eagles recover for another red zone turnover, a theme that has been very prevalent on that side of the ball in recent weeks.

Let's take a look at another shot, and another example of great technique that results in another defensive stop from this front line.

It's first-and-10, and the Eagles are in their base defensive front. On the far left you see Barwin, with Cedric Thornton lined up over the right tackle, Bennie Logan over center and Fletcher Cox over the left tackle.

Off the snap, look at the technique shown by Logan and Cox. This ball is coming right at them, and they stand both of their opponents up at the line of scrimmage and hold them at the point of attack. Both have their hands inside, and are two-gapping to perfection on this play.

They both disengage from their blocks and converge on Bell for a short gain. Notice the two shadowy figures collapsing on the other lighter shadowy figure inside the circle (thanks Mother Nature for making this film review so easy to break down).

As usual, even through the snow, the Eagles used a variety of stunts and games up front to help create penetration in the backfield. This time, we have a simple tackle/end stunt with Cox collapsing inside and Logan looping around to the C gap.

Cox completely destroys this play for the Lions, as he drives his assignment 3 yards into the backfield. The back evades the pressure, but to no avail.

He spins right into the arms of Logan, who came free on the stunt. Look at all the bodies running to the ball. The Eagles defense once again played with fanatical energy throughout the game, constantly running to the football and playing with enthusiasm. Chip Kelly has talked about it in the past, and that's if you can get your players to play with great effort and energy, and the technique follows, you're going to be in good shape defensively. That's exactly what has happened with this group.

It wasn't just the starters who stood out against the Lions, as the backups made a number of plays in the run game as well. Let's take a look at another play a bit later in the game.

This will be the same split zone run. It's one of Detroit's staples in the run game.

At the snap, look at the job Curry does dipping his shoulder and penetrating into the backfield.

That, combined with Graham's ability to evade the wham block from the tight end crossing the formation, stops the Detroit running back for no gain on second-and-1.

It wasn't just the run game. The Eagles defense held Lions quarterback Matthew Stafford to a pedestrian 148 yards through the air. Obviously, the weather contributed, but it wasn't just the elements that limited the Pro Bowl passer.

It's second-and-8 in the third quarter, and Stafford is in the shotgun. At the top of the screen, Calvin Johnson runs a deep post. At the bottom, receiver Kris Durham runs a comeback route. Inside, there are two in-breaking routes, with the shallow cross from Brandon Pettigrew (the blue arrow) as Stafford's initial target. The wind inhibited most downfield passing throughout the day, and the physical tight end should be able to pick up some yardage to set up at least a manageable third down play for Detroit.

After the snap, linebacker Mychal Kendricks read the crosser perfectly, as he drives down on the route and bumps Pettigrew off course. Stafford has to look elsewhere to get rid of the football.

But who else is open? You see a double team up top on Johnson, two more defenders in the slot against Nate Burleson and at the bottom of the screen Barwin is squatting to prevent a throw to the comeback as well as to the crosser. Stafford has nowhere to go with the football, and is forced to tuck it as he stumbles for a 1-yard gain. This was a great job of assignment football by the Eagles defense. Everyone did their job to keep a dangerous Detroit offense from producing at a high level.

Fran Duffy is the producer of the Eagles Game Plan show which can be seen on 6abc Sundays at 11:30 AM. 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.