San Francisco-Denver: Peyton who? 49ers’ run game will be key to beating Broncos

There’s no doubt the Denver Broncos are better this season on defense than they were a year ago.

In 2013, the Broncos finished the season ranked 22nd in the NFL in points allowed per game, but this year they’re allowing just over 20 points per game, which ranks seventh. Though they ranked 16th in yards per play a season ago, they’ve jumped up to third in the league at 4.7 yards per play allowed in 2014.

But their defense had a setback when they lost their top linebacker — again — to a leg injury. After already missing several weeks early in the season, Danny Trevathan will be out for several more after getting hurt in last week’s game. The Broncos will rely on Brandon Marshall (four NFL starts) and rookie seventh-round draft pick Corey Nelson on Sunday night to stop the NFL’s seventh-ranked rushing attack led by Frank Gore of the San Francisco 49ers.

The 49ers have had one of the NFL’s best rushing attacks since Jim Harbaugh took over as coach in 2011. During that span, the 49ers are 32-5-1 when rushing for 100-plus yards (only the Patriots have been better in that category). But they’re not invincible.

Despite losing to the 49ers on Monday night, the St. Louis Rams (ranked 26 out of 32 versus the run) had a formula for stopping the 49ers, and it proved effective as they limited them to just 89 yards rushing (only 10 in the first half). The Arizona Cardinals are one of two teams that have beaten the 49ers this season, and they’re the only team to hold the 49ers to fewer yards on the ground this season (82) than St. Louis.

NFL WAGs

Let’s break down St. Louis’ approach and what specifically makes San Francisco tough in a little more detail to see what Denver needs to be aware of to survive the Niners’ attack.

The Rams’ plan vs. San Francisco

What was the Rams’ formula? Load the box to stop the run.

The problem for the Rams, though, was how that affected their passing defense. When St. Louis put an extra defender in the box to stop Gore and Co., their cornerbacks found themselves in one-on-one matchups with 49er wide receivers Anquan Boldin, Michael Crabtree, Stevie Johnson and Brandon Lloyd. Colin Kaepernick connected with this fleet for 343 yards, three touchdowns and an eye-popping 15.6 yards per reception. Rams defensive backs didn’t rise to the challenge to win matchups like Crabtree did here:

That double move was an example of one of the "games within the game" that we can watch on Sunday when the 49ers face the Broncos: San Fran’s wideouts against Denver’s cornerbacks in one-on-one matchups.

NFL POWER RANKINGS

It’s likely that Denver will follow St. Louis’ formula for stopping the run — loading the box to add an extra defender for the ground game — and that means cornerbacks Aqib Talib and Bradley Roby will have to rise to the challenge and win mono-y-mono confrontations with San Francisco’s wide receivers. Denver’s cornerbacks are more talented than the those the 49ers faced on Monday night, so those matchups will be much more fun to watch. The Broncos’ cornerbacks have an NFL-best 22 pass breakups in 2014.

The matchup that I’ll be watching more closely, however, will be Denver’s linebackers against San Francisco’s running game.

San Francisco is as good as anyone in the league at getting defenders out of position — and out of their run gaps — which is a big part of the reason it is averaging more 135 yards rushing per game. Whether Denver’s linebackers are disciplined with their run keys will be one of the most vital determining factors in the game.

Now let’s look closer at some of the run schemes with which San Francisco has success — specifically the runs that can challenge inexperienced linebackers like Denver’s Marshall and Nelson.

Pulling linemen

Pulling offensive linemen is one way the 49ers get defenders out of position — and out of their run gaps — after the ball is snapped. Linebackers are taught to rely on their keys — the center and both guards — to take them to where the ball is being run. The first run highlights the type of misdirection plays San Francisco used to gash the Eagles for 218 yards on the ground a few weeks ago. Here’s how it’s drawn up:

In the next photo, while the blocking cavalry for the 49ers are already well on their way to the point of attack to the right of the screen, you can see the linebacker missed his keys and bit on a jab-step fake to the left by the running back.

In the NFL, just one bad read and false step by a linebacker can result in a big run play for the offense.  

More than in most weeks, it will be vital that Denver’s linebackers read their keys to take them to the run. The Eagles’ linebacker didn’t do that here — he reacted to the run after it was too late — and it allowed Gore a big gain.

HOT UNDER CENTER

If he had read his keys, they would have led him straight to the play.

Unbalanced formations

Another way San Francisco will try to attack Denver in the running game will be with unbalanced lines. The 49ers do it as often as anyone in the NFL, but will double down this game given the inexperience of the Broncos at linebacker.

While pulling linemen when the ball is snapped is one way to get the defenders out of position and their run gaps, unbalanced formations are designed to get the defense out of position before the ball is even snapped.

Let’s take a look at an example of how an unbalanced formation can create problems for a defense.

You can see in the previous photo that Dallas had five defenders to the strength of the 49ers’ formation (to the right of the dotted red line) including the extra hitter, giving it eight men in the box to stop the run.

The problem for the defense occurs when San Francisco’s right tackle shifts before the snap (yellow dotted line) to create an unbalanced line — and ultimately changes the strength of the formation. Let’s see how the defense adjusted and aligned after the shift:

The Cowboys did not get aligned properly to this unbalanced set. Both linebackers and the safety should have shifted over one more gap (red arrows) to account for the shift, but they didn’t.

There are now four defenders to the weak side of the formation. Here was the result:

This play ended up being a 20-yard explosive gain for Gore. The Cowboys had four players to the weak side of the formation and the play, while the 49ers outnumbered Dallas six to four on the new strong side of the formation after the shift to an unbalanced set.

Those are just two examples of why San Francisco has been one of the NFL’s most successful rushing teams the past several years under Harbaugh. It’s one of the most challenging run games to defend because it often forces players into mental errors — getting misaligned and out of position. I didn’t even touch on the added problem that Colin Kaepernick causes with his ability to be a force in the run game, too.

With Peyton Manning calling the shots for the Broncos, they’re going to put up points. That being the case, all Denver has to do is play disciplined on defense. That all starts with reading keys in the run game.

If Denver’s linebacker corps does that on Sunday, it will win enough downs and play well enough to get the win. If it doesn’t, it will be inviting one of the NFL’s toughest run games to have its way.