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49ers vs. Eagles preview: Battle of the deep ball

The 49ers are looking to escape September with a .500 record when they host the Eagles on Sunday and to do so, they must put a lid on Philadelphia's vertical passing attack.

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Matt Kartozian-USA TODAY Sports

A must-win game in September? Blasphemy. When the San Francisco 49ers host the Philadelphia Eagles on Sunday, the fate of their season will not be decided. But golly, a win sure would be nice.

In the first quarter of the NFL season it’s important not to focus too much on wins and losses but rather a team’s underlying performance. Going 4–0 is fantastic, but if that team is squeaking out wins, getting an extreme share of the fortunate bounces, and generally not playing like a 4–0 team, chances are they will be exposed over the final 12 games of the season (see: Arizona Cardinals, 2012 ). The inverse holds true as well. A team capable of outscoring opponents 59–16 in the first half of games — like the 49ers have — but somehow finds themselves looking from the bottom up in the standings are likely to see that level of performance begin to show through over the full 60 minutes.

That said, San Francisco does risk digging themselves too deep of a hole in what is sure to be a crowded NFC playoff picture. After three weeks, the 49ers have already dropped to 12th among NFC teams in Football Outsiders’ playoff odds, behind three teams sharing the same 1–2 record (New Orleans, Green Bay, Washington). This is partially due to the strength of the NFC West and the more difficult path San Francisco has to win their division, but another loss to an NFC team this week and the 49ers could find themselves on the wrong side of too many playoff tiebreakers, even if they do manage to turn things around.

So with the 49ers facing a would-be-really-nice-to-have-it game on Sunday, let’s look at some of the key areas that will decide their fate against the Eagles.

Deciphering Philly’s Run Game

The foundation of Chip Kelly’s offense is the running game, specifically the inside zone. It’s a play the Eagles’ offensive lineman spend nearly half of their practice time working on and the blocking scheme pervades Philadelphia’s entire offense, not just the running game.

Kelly rode the inside zone to the best running game in football a season ago. LeSean McCoy and Kelly’s scheme certainly deserve a lot of credit, but a significant reason for the success of Philadelphia’s offense was the offensive line. Filled with talented, athletic players up front to carry out Kelly’s preferred scheme, the Eagles were fortunate enough to start the same five players along the offensive line for all 16 games a season ago. Continuity is a huge factor for the success of an offensive line and when you combine that with All-Pros like Evan Mathis and Jason Peters, the results are devastating.

The Eagles have not been so fortunate in 2014, getting a lesson in how real injury regression can be in the NFL. Of the five starters from a season ago, just two will be on the field Sunday against the 49ers: Jason Peters and Todd Herremans. Peters will man his typical left tackle spot, but Herremans is being forced to kick-out from guard to the opposite tackle position. Herremans has played right tackle previously, but is a far more effective player inside.

As you might expect, all of that reshuffling up front has caused Eagles’ running game to suffer. LeSean McCoy hasn’t gone anywhere and the league’s shiftiest player is still getting every yard available to him on most plays. But that remarkable rushing attack from a year ago has nose-dived, ranking 29th in run offense DVOA through three weeks. Philadelphia was held to 2.2 yards per carry a week ago against Washington and even that paltry number was propped up by an 18-yard run from Darren Sproles. That run ended with a Sproles fumble, showing that the Eagles just can’t have nice things in the run game right now.

So do the 49ers treat the Eagles’ run game as the league’s best attack from a season ago or is Philadelphia’s depleted offensive line and ineffectiveness to start 2014 enough to change the game plan? It will be interesting to see how Vic Fangio and the 49ers choose to answer that question.

It’s well known that the Eagles love to spread things out. Fangio would typically match that type of offense by using a heavy amount of the 49ers’ nickel — and increasingly this season, dime — package. However, against teams that can effectively run the ball from those spread looks, such as Seattle, Fangio will mix in more of San Francisco’s base 3–4 defense, especially on early downs. Prior to the season, I would have expected more of the latter approach from Fangio in this game. But with the struggles Philadelphia has had producing consistent yardage on the ground this season and all of the absences along the offensive line, Fangio might be confident his sub-packages can get the job done.

Chicks Dig the Deep Ball

The 49ers pass defense has been a mess through three weeks. The pass rush currently begins and ends with Justin Smith — who has three of San Francisco’s four sacks on the season — and while Smith has continued to be a very effective player despite his advancing age, he’s not exactly the guy you want as your marquee pass rusher. The absence of a pass rush has left San Francisco’s secondary — a weak spot coming into the season — exposed and opposing quarterbacks have taken advantage.

Both Chicago and Arizona got things rolling on offense once they started taking shots down the field. It’s unlikely that we’ll see Philadelphia wait as long to test San Francisco’s secondary deep. According to Pro Football Focus, only Drew Stanton — with his one start last week — has attempted a higher percentage of his throws 20 yards or more downfield than Nick Foles (21.1%). Foles has struggled a bit in both finding open players downfield and making accurate throws when he does so far this season. However, Foles was one of the league’s most effective passers on deep passes last season and I would not count on those struggles continuing for much longer.

Chip Kelly’s preferred method of attacking downfield is with four verticals. Just as the name implies, the play gives Foles four receivers running deep down the field, each running to specific landmarks in order to stretch the secondary. Running up the seams are typically rookie Jordan Matthews (6’3") and tight end Zach Ertz (6’5"), giving Foles big targets down the middle of the field. On the outside, Jeremy Maclin provides the ability to run by opposing cornerbacks if defenses start cheating their safeties towards Matthews and Ertz in the middle.

If the first three weeks are any indication, it’s a play San Francisco’s secondary is going to struggle defending. Brandon Marshall and Michael Floyd are two big wide receivers that have given the 49ers problems already this season, particularly when lined up in the slot, as Matthews and Ertz will be often on Sunday. If the 49ers have any hope of shutting down the Eagles deep passing game, they must do so before plays have a chance to develop by getting pressure on Foles.

Recognizing the 49ers inability to rush the passer by bring just four, Fangio increased his blitz frequency against the Cardinals. After rushing five or more defenders just 9.1 percent of the time (8-of–88 drop backs) through two weeks, per ESPN Stats and Info, Fangio dialed up the blitz 31.6 percent of the time (12-of–38) in Arizona. The results were encouraging as the 49ers held the Cardinals to just 2.25 yards per play and two first downs on the 12 snaps San Francisco brought pressure. The issue was penalties; four of those plays were cancelled due to a penalty from San Francisco’s defense, several of which had no impact on the success of the blitz.

If the 49ers can stop shooting themselves in the foot with penalties — and there’s plenty of reason to believe they will — we should expect to see the 49ers continue to blitz more frequently until Aldon Smith returns, especially in key situations such as third downs and in the red zone when they’re looking to get off the field.

Pass Heavy 49ers?

Those who found themselves offended by San Francisco’s run-pass ratio against Arizona might want to avert their eyes this week, as there’s a strong chance we will see Harbaugh and Roman continue to lean on the passing game.

If there’s one thing that Philadelphia does well on defense, it’s stopping the run. The Eagles have had the league’s third-best run defense through three weeks, and while that’s probably giving them too much credit (Thanks, Jacksonville!), it’s clearly the strength of their defense. Much like the 49ers, their issue on defense is defending the pass.

Philadelphia’s pass rush been atrocious. The Eagles have just three sacks on the season and their 2.6 percent Adjusted Sack Rate is the worst mark in the league. Bookend pass rushers Trent Cole and Connor Barwin have combined for just a single sack in 2014 and there’s been no one else to pick up the slack. This has left Philadelphia’s porous secondary vulnerable down the field (I’ve heard this before…).

Philadelphia struggled adjusting to late shifts and motions from Washington’s offense a week ago, especially when Washington would motion to some sort of bunched or stacked alignment by the receivers. Miscommunication from Philadelphia’s secondary in those situations gave Kirk Cousins several easy throws to open receivers.

Using shifts and motions to create an advantage pre-snap has been one of San Francisco’s biggest strengths under Harbaugh, consistently getting favorable match-ups on the inside in the passing game because of them. Shifts and motions late in the play clock — while maddening for fans at times — gives the defense little time to adjust and can lead to blown coverages and missed assignments if the defense isn’t proficient in communicating those last-second checks. The 49ers have spent a good amount of time simply spreading things out and keeping the formation idle prior to the snap this season. Expect that to change against the Eagles.

San Francisco’s passing offense has relied more on the short passing game in 2014, especially against Arizona with Vernon Davis out of the line-up. The quick throws have been a boon to Colin Kaepernick’s completion percentage, but without Davis the 49ers don’t have anyone that can consistently stretch the defense. San Francisco has just one receiver in the top 50 in yards per reception this season, with Stevie Johnson just sneaking into that group at 12.5 yards per catch. The vertical element Davis brings to the offense not only can provide big chunks of yardage, but will help ensure those passing lanes underneath stay open for San Francisco’s other targets. If Davis is able to go this week (a game-time decision as of this writing), the 49ers passing offense should be in for a big day.

Prediction: 49ERS (–5) over Eagles