Keys to the game: Niners-Eagles -- Part I

Can the Niners find an 'edge' in the run game?

The Philadelphia Eagles are a juggernaut. They ran through the NFC and have been considered a top team for much of the season. Their head coach gives great interviews, they convert seemingly every fourth down, and their staff will be poached to fill positions around the league this offseason.

On Sunday, the Eagles face off against the San Francisco 49ers at Lincoln Financial Field. The 49ers find themselves in their third NFC championship game in four years while trotting out their third quarterback of the season. San Francisco hit their stride after adding Christian McCaffrey, and the run game has popped both on film and on the advanced stat sheet. Coincidently, one of the very few places the well-rounded Eagles may be considered “weaker” is in run defense. The 49ers will be their biggest test of the season on the ground, and Kyle Shanahan will surely have his best drawn up for this one. The Eagles’ stylistic choices in defensive construction help inform how San Francisco may design this week’s run game call sheet.

The Eagles subscribe to a modern theory of defense that has been spread across the league thanks in no small part to Eagles defensive consultant Vic Fangio. They play with light boxes, two high safeties, and want to force the offense to make the correct decision time after time going down the field. Philadelphia wants to encourage teams to run the ball in suboptimal ways and take advantage of offenses that are uninspiring on early downs and end up in third and long. 

On their way to a league-best 14-3 record, the Eagles’ defense ranked 4th in EPA/play. However, they drop to 23rd when it comes to rushing EPA/play and rushing success rate. The sound you hear is Kyle Shanahan scribbling up exactly how they will attack the Eagles’ run defense.  

At all levels of football, offenses search for angles, leverages, and open space in the defense. The A gap (the area between the center and the guard) is not particularly popular as interior defensive linemen and downhill linebackers can create zero-yard rushes in a hurry. The B gap (the area between the offensive guard and offensive tackle) is ripe for attack when open. An open B gap can allow for linemen to work their double teams to the second level with better angles while getting a running back into open space quicker.

Shawn @syedschemes

Dalvin Cook's long TD run on zone weak to the B gap bubble: -Vikings come out in 12p heavy -C and LG double to 58 -Jefferson sees the rotating S and does a great job sealing -Cook has to be his own blocker for 1 guy then is able to erase the S's angle

Four down fronts generally set one lineman, a three-technique, in the B gap. The other interior defensive lineman often ends up closing the A gap. One way to set a four-down front is with the three-technique to the running strength of the formation to discourage attacking the B gap bubble to that side. This means the precious B gap bubble is now on the offense’s weak side.