Every football season has a handful of games that are billed as "the biggest regular season game of the year" in the week leading up to kickoff. So far this year, the San Francisco at Seattle Sunday nighter and Peyton Manning’s return to Indianapolis were both promoted as such, before being quickly forgotten. Now, it’s time for Kansas City and Denver to step into the national spotlight for what seems like the biggest game of 2013 to date.

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This game certainly has no shortage of storylines. Are the Chiefs for real? How’s Peyton Manning’s ankle? Will Von Miler break Derrick Thomas’ single game sack record as every Kansas City fan curses Eric Fisher in between heavy sobs? There are also plenty of matchups, such as Manning’s stats vs. Alex Smith’s wins and the Broncos' star-studded offense vs. the Chiefs' loaded defense.

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There’s a lot at stake here, and there are plenty of angles to write about to be sure. But my focus is on the most important factor Sunday: Which team is able to take away their opponent’s running game and limit the big plays they create off of it.

These two offenses may seem different, but their play calling patterns are actually pretty similar. Both offenses are fairly conservative in the sense that they are designed to avoid negative plays and stay on schedule on the early downs. Both rely on short passes and runs to create third and shorts. You won’t see a lot of seven-, or even five-step drops on first down. When the teams do get a big play, it’s usually the result of a designed shot from an ideal down and distance (often 2nd and short from around midfield). They are very calculated.

That’s why the team that can control the other’s running game and force the issue on second down has the advantage. If either defense can stop how the other team wants to run, not only do they force the offense out of their comfort zone, they also take away most big shots against their defense. Here’s how each team wants to run it, and what the other will need to do to try to stop it.

When Kansas City has the ball:

The Chiefs have the more traditional NFL running game. They run a little bit of the gap/man scheme plays but rely primarily on inside and outside zone running schemes. The Chiefs have been effective running the outside zone or zone stretch play ever since Jamaal Charles broke into their backfield in 2009. Despite three different head coaches since then, the Chiefs best and base running play has remained the same. The coincidence in this matchup is that it was the Broncos that made this zone stretch scheme famous in the 1990s, using their undersized offensive line blocking for Terrell Davis and a bunch of other backs that all seemed to exist for the sole purpose of ruining your fantasy league.

There are two real ways the Chiefs make yards on their favorite play. The first is through Charles getting to the edge very quickly and outrunning the defense. This sounds simple, but it relies on Charles aiming for the outside shoulder of the edge defender as the back receives the ball. He runs in a straight line that direction, if the defender doesn’t jump out and keep contain, then Charles just stays on his course. When it works like this, it looks like the simplest play in football.

Both times the defensive end is completely wrong for getting hooked by Kansas City’s left tackle (and best offensive lineman) Branden Albert, but that’s what it looks like when defense lacks any semblance of gap integrity. The funny thing is, that despite being called outside zone, the play isn’t really designed to hit outside the tackle box like that.

The play is really set up to make the defense think the play is going outside before the running back sticks his foot in the ground and carves up the middle of the defense for big chunks of yards.

That is how the play is really designed to look, with the exception of the missed cut block by the right tackle. The play side of the offensive line gets their defenders moving laterally, while the backside tries to cut their men off to create a giant seam down the middle of the defense. Here, even though right tackle Donald Stephenson missed his cut block, he creates enough of a lane just by throwing himself at the defender’s legs. He doesn’t block him, but he slows his man down enough to allow Charles to explode through the hole. It's a gorgeous play when it’s run right.

One of the reasons Charles was able to get outside so easily in those first two GIFs is that teams are so used to this being a play designed to cut back -- K.C. can actually catch them off guard by just running straight outside. It’s probably why the Chiefs have had so much success over the years with this play. Charles -- more so than just about any running back in the league -- not only wants to run outside but has plenty of speed to get there. So if the defensive end cheats the play and hangs inside at all, Charles will go whizzing by him and the end will head to the bench to get a yelled at by his coach.

So, how do the Broncos go about slowing down the Chiefs' run game? It starts with their outside linebackers, Shaun Phillips and Von Miller. The key to stopping the stretch play is for the defense to set the edge. If the end man on the line of scrimmage for the defense can penetrate up the field while maintaining outside leverage, he creates a pile-up effect. That pile-up makes the runner cut it back too soon, while the rest of the defense is still in their gaps, and the whole thing looks like a giant mess.

You can see in that play above that Giants defensive end Justin Tuck gets off the ball quickly and knocks Albert into the backfield a couple of yards. Just as importantly, Tuck maintains his outside leverage the entire play so Charles has no choice but to cut it back early into a very gap-sound defense. That’s a perfect example of setting the edge.

The Broncos are actually very well equipped to have continued success on the edges vs. K.C. Their outside linebackers play with great quickness off the ball and are consistently in the backfield before offensive tackles can engage them. On top of that, their inside linebackers are really great at coming downhill and taking on blocks in the hole. This play from the first quarter of the Chargers game demonstrates this.

Just like Tuck, Shaun Phillips does a great job of setting the edge here. He explodes off the ball and is a yard-and-a-half deep in the backfield by the time that the left tackle gets to him. That forces an immediate cutback from Ronnie Brown (who probably can’t beat anyone to the edge anyway). Phillips recognizes the play as it develops and does a nice job of throwing the left tackle outside and coming in to make a play. He actually doesn’t make the tackle, though, because the tackle grabs him, although somehow no hold was called. Still, a really nice play by Phillips flag or no flag.

Another key to Denver's run defense is Danny Trevathan. He’s not a household name, but he has good instincts in the running game. In the above GIF, he recognizes the play quickly and meets the fullback right on the line of scrimmage in the middle of the hole. The difference between meeting that lead blocker in the hole and even just a yard later is tremendous. If Trevathan is a little slow to the hole here, even if he stands the lead blocker up, Brown can squirt to either side of the block. But by engaging the block in the hole, Brown has to just try to lower his head and gain as many yards as possible by falling forward.

If the Broncos can get that kind of play from their linebackers consistently, they have a very good chance of shutting down K.C.’s base running game. That’s not to say that the Chiefs are going to be stuck relying on Alex Smith airing it out 40 times -- there are some things that Kansas City can do to take advantage of Denver’s edge rushers and aggressive downhill linebackers. There was one play the Chargers ran that the Chiefs should absolutely steal.

It was an outside zone concept where the right end and fullback switched responsibilities. The Chargers had their tight end arc release immediately to the safety and they left the defensive end for the fullback. Here’s what it looked like.

Von Miller feels Antonio Gates running absurdly wide and rightly abandons hope of staying outside him to start penetrating up field. He sees the fullback coming at him and I likely assumes the fullback is going to try kick him out, so Miller tries to wrong-arm it (rip underneath it with his outside arm) and spill it outside. At the last second though, Miller sees what’s happening and redirects outside and forces a hold. But if the fullback doesn’t hold Miller, and just gets a decent block, the Chargers have a big play.

I’m guessing the Chargers saw that that the Broncos edge guys like to penetrate up the field early and come underneath late (just like Phillips did in that earlier play). This play does a great job of taking advantage of the Broncos aggressiveness by allowing Miller to rush up the field and hope he jumps inside, without really changing what the Chiefs would do.

The other thing the Chiefs need to do is try to take advantage of how aggressively Denver closes distance up front. Denver’s defense is really good at eating up space vacated by blockers. By that I mean that if the man closest to them moves away, the Denver defense will close down aggressively and constrict room from the offense.

Aggression makes a defense susceptible to misdirection plays. Kansas City has done a good job of using bootlegs and half roll-outs off their outside zone game to create shots down the field. If the backside defenders on Denver’s defense start tackling Charles on running plays away, don’t be surprised if Smith keeps it and unloads one down the field.

In that clip above, the defensive end is closing down the line of scrimmage aggressively because he has to maintain his gap and negate any cutback lanes from Charles. He can afford to be that aggressive because if Charles tries to cut it all way back outside of him, the safety should be right there. But when Smith keeps the ball on a pass play, the safety has to stay in coverage and now no one has contain. That allows Smith to just post up in the pocket and scan from left to right deep down the field without any pressure.

But again, this isn’t the type of play Kansas City will run on the vast majority of their early-down situations, so if the Broncos can shut down the base plays, they don’t have to worry about the elaborations off of them as much.

A final thing Kansas City should try is a little of the triple option they ran against Dallas earlier this year. With the way Denver’s outside linebackers play, I can just about guarantee that Smith will get a pull read and I think they’ll have a 2-on-1 on a corner. Just something to look out for.

When Denver has the ball:

Denver’s running game is very different from Kansas City’s, but it can be equally effective. The Broncos attack isn’t particularly complicated. They run a lot from shotgun and they tend to lean on inside zone with the occasional single back power or outside zone.

Whereas the key to K.C.’s running game is forcing teams to respect Charles’ ability to beat you outside at any time, the key to Denver’s running game is that they always go where they outnumber the opposition. Denver will spread a defense out and if the defense doesn’t spread out with them, Denver will throw. If the defense does spread, they’ll run. The Broncos may be the only team in the NFL that consistently has not one, but two more guys in the box than the defense has.

That’s an eight-man to six-man advantage in favor of the offense in the above GIF. People have been talking about the emergence of Knowshon Moreno, but it’s been more the disappearance of box defenders that has charged the Broncos running game. There are a lot of running games that would look pretty good playing eight-on-six.

The problem with only running it when you have a clear numbers advantage is that you’ll probably end up throwing it too much. Peyton Manning is great and I’m not sure anybody has a better group of receiving threats, but if you start throwing 50-60 times a game you’re going to see too many second- and third-and-10s. So the Broncos have done what a lot of teams are doing and started using wide receiver screens as substitutes for running plays. It’s a high-percentage completion where it’s hard to end up with anything worse than a few-yard gain, so from a drive-planning standpoint, there is virtually no difference between a wide receiver screen and handing the ball off.

It’s not that the Broncos are the first ones to think of this concept, college spread teams have been doing it for at least 15 years now and the 00’s Patriots were also very fond of these types of plays. It’s just that Denver is executing them better than anybody else right now. One screen they’ve been particularly great with is a tunnel screen to Demaryius Thomas out of a trips formation.

There really isn’t much to explain here. The Broncos receievers do a nice job of blocking on the outside and the linemen hustle and move well enough to make a couple of downfield blocks. In both of these cases, the Broncos have advantageous looks from the defense, but that’s the point. If the Broncos don’t have the numbers outside, they can just change the play and hand it off to Moreno.

The one area where they are really ahead of the curve is using their wide receiver screen game to set up passing plays down the field. If wide receiver screens are truly a running game substitute, it would make sense that you should be able to fake them and take a shot deep. Isn’t that how the forward pass was first used, as a high-reward gamble occasionally taken to keep the defense honest?

The Broncos are the first team that has done this consistently. In particular, the Broncos have run these plays in situations and areas of the field where play action passes have always been popular.

That play is from the Broncos first game of the season. They ran it the first play after getting a turnover. Coaches love taking play action shots to the end zone the first play after a turnover, and the fact that Denver went with a fake screen just furthers the theory that their screen game is just a more explosive version of running game.

The play itself is essentially just double verticals from the two inside receivers. It’s a play that Denver has used a couple of time this year, and one they particularly like on the fringe of their opponents' red zone between 20-35 yard line.

There it is again versus the Jaguars, but with Wes Welker playing the role of Julius Thomas. The personnel adjustment is something good teams do, so they can keep running their best gadget plays (I would consider a fake screen a gadget play still) without tipping off the defense.

You’ll notice each of those last two plays came from Denver’s side of the field, which is where Denver starts taking their shots. Manning may throw deep occasionally on his side of the field, but it’s typically off quick drops on seam routes where there are plenty of shorter options. Denver will usually wait before they call up something that is down the field or check down.

So, how does Kansas City take away Denver’s run game? Defensive coordinator Bob Sutton is going to have decide how he wants to try to force the Broncos to beat them. The Colts had some success playing a lot of press man with a two-deep shell versus Denver. It messes up the timing on Denver’s short routes, and it’s really hard to run wide receiver screens against press man. The problem is that the very first GIF I showed from the Broncos offense (the run to Moreno) is from when a defense played that coverage.

The Chiefs have the luxury of changing up their looks. There are plays where you show a sparse box and dare them to run and challenge your front seven guys to hold up. What’s the point of having Dontari Poe, Derrick Johnson, Tamba Hali, and Justin Houston if you can’t rely on them to win some individual matchups and beat an occasional double team? They play shorthanded inside on first downs and hope they can keep Moreno under four yards consistently there.

Their secondary has guys like Eric Berry, Brandon Flowers, and Sean Smith. Those are big, physical players that should be able to press and run with the Broncos, and K.C. shouldn't be afraid to leave them alone on the outside particularly in second-and-long situations. Make the Broncos complete a pass to avoid a low-percentage third down, and certainly don’t let them give it to Moreno for an easy three yards.

One thing I don’t expect to see a lot of is blitzing. I think the Chiefs greatest strength on defense is their ability to generate pressure with just four rushers, particularly if three of those four are Poe, Houston, and Hali. If they can do that to Manning, they have a great chance of slowing Denver down.

Producer: Chris Mottram | Title Photo: Getty Images Getty Images