On Sunday night the New England Patriots allowed a season high 179 rushing yards against the Denver Broncos. In fact this was the first time the Patriots defense allowed 100+ yards on the ground since the week 6 matchup against the Indianapolis Colts (who got 35 scrambling yards from Andrew Luck). The way the Broncos were running on the Patriots reminded some of last year's divisional playoff game against the Baltimore Ravens - which is no surprise since the Broncos' head coach Gary Kubiak was the Ravens' offensive coordinator last year.
The Broncos' Zone-Blocking Scheme
Gary Kubiak's teams are known for their focus on the ground game. Last season under his offense in Baltimore Justin Forsett rushed for 1266 yards out of nowhere. Before that he coached Arian Foster to three consecutive 1200+ yard seasons in Houston. And during his time as the Broncos' offensive coordinator it seemed like anybody there could be a 1000 yard rusher. A lot of this has to do with the blocking scheme his teams run - the zone-blocking.
Trying to describe the system in a simplified way: Whereas most teams run the ball by pushing downfield zone-blocking teams move horizontally to one side first. The target is to stretch the defense until it breaks and opens up a cutback lane in the middle of the field. The principle behind it is fairly simple and indeed, most of the Broncos' running plays look absolutely identical:
The Broncos move their entire line towards one sideline. The center and the guard to which direction the play will go double-team the defensive tackle while everybody else is blocking one-on-one. To take care of the linebackers most times the tackle on the weak side will pull while one of the double-teaming linemen will release into the second level after pushing the defensive tackle out of the picture. In order to prevent the defensive linemen on the weak side from chasing down the play the offensive lineman and tight end there are asked to cut them to the ground.
Examplary for this is the third running play of the game for Denver (at the same time their first real gain on the ground). The entire offensive line moves towards the left side. Patriots' defensive tackle Akiem Hicks is doubled by the center and left guard and pushed to the sideline. Chandler Jones and Alan Branch are taken one-one-one while tight end Virgil Green is trying to bring down Jabaal Sheard. The remaining lineman, right tackle Michael Schofield, is pulling.
This blocking scheme can be taxing on a defense not accustomed to seeing it on a regular basis since the defensive players can't act on instinct and fly to the direction the blocking is going. It's especially putting a severe strain on the attention of the linebackers who must not overpursue. Which is exactly what happens on this play:
Patriots linebacker Jonathan Freeny gets sucked in too deep and a cutback lane for C.J. Anderson opens up for a gain of at least four or five yards. The Broncos' running back adds another four yards on top of that by executing a great spin move around Dont'a Hightower.
Another example of Freeny overpursuing is this play in the fourth quarter that resulted in a nine yard gain. The linebacker gets sucked towards the right side even though there is no running lane opening up there, leaving a hole for Ronnie Hillman to go through. Jerod Mayo on this play is actually in a good position to stop Hillman for a short gain but (a recurring theme) is a step short and can't wrap the running back up.
But Jonathan Freeny was not the only linebacker to committ this mistake. Even an experienced player like Jerod Mayo got caught out of position like on this nine yard gain by Hillman - the first running play after Dont'a Hightower left the game and at the same time the first significant gain for Hillman in the game.
But the linebackers aren't the only ones having to fight instinct. Likewise the linemen on the line of scrimmage have to pay attention and can't just randomly push into the backfield. If they do that on the back side they'll take themselves out of the play while opening up a rushing lane and freeing blockers downfield, like Akiem Hicks on this play:
How Can It Be Stopped?
Aside from the obvious method of maintaining great discipline across the front seven it is possible to blow up that scheme at the line of scrimmage by good play from the defensive linemen facing the double-team. Against the Broncos it was the first round pick Malcom Brown who highlighted that.
The first way a defensive lineman can disrupt the play is holding up the double-team (easier said than done). To prevent the linebacker running to the side of the play from bottling up the rush it is important for one of the double-teaming offensive lineman to release into the second level as soon as the defensive tackle has been pushed to the side. On the play above Malcom Brown is holding up the center and left guard with one arm each so they can't release and block Jonathan Freeny flying to the line of scrimmage. The result is Hillman getting tackled by Freeny for a gain of only one yard (also helps that Ninkovich was able to shed his block).
A second way to impact the run is to attack the shoulder of the center in the direction of where the play is going right off the snap, before the center can release for the double team and push him back. On this 2nd and 4 late in the first quarter the rookie defensive tackle is doing just that. With the entire line heading towards the right sideline the guard can't help out the center. Combined with Rob Ninkovich setting the edge the Patriots wall off C.J. Anderson in the backfield. The Broncos' running back manages to get around Ninkovich but by the time he is there other Patriots defenders have already arrived to stop him short of the first down.
Yet another way to disrupt the double-team is by attacking the guard to which direction the play is going off the snap and push him into backfield before the center can establish the double-team.
Doing so breaks the offensive line going to the sideline and the center can't push the defensive tackle to the sideline without opening up a lane for the linebacker to storm through. If the defensive end can set the edge the running play is bottled up. (Malcom Brown actually followed up this play with a similar one a few minutes later, stopping the Broncos for a loss in addition to drawing a holding call on a struggling Evan Mathis.)
The Big Plays
At this point the big touchdown runs of 19, 15 and 48 yards still haven't been talked about. Scheme-wise there isn't much to analysed. It basically all comes down to missed tackles during the first two runs and a good/bad playcall on the game-winning run in overtime.
On the first touchdown run in the second quarter the Broncos are not running their usual zone-blocking scheme, but rather a sweep play to right side. Jerod Mayo has a free lane to the running back but comes up a split-second short and misses the tackle at the line of scrimmage. One can't help but think that a healthy Hightower or Collins would've arrived there earlier to bring Hillman down.
During C.J. Anderson's 15-yard run after Chris Harper's muffed punt the Broncos are again not running their zone-blocking but rather a standard run up the gut. The Patriots defense shuts down the middle and Anderson cuts to the outside with Devin McCourty missing the tackle at the line of scrimmage. With the snowy conditions neither Patrick Chung nor Logan Ryan can tackle the running back before he runs past them.
Meanwhile on the game-winning touchdown run the Patriots are in a bad defense to stop the sweep play to the left side. The Broncos bunch up their receivers on the left side and Jonathan Freeny and Patrick Chung are lined up directly at the line of scrimmage. This puts the pressure of getting to the outside in time on Devin McCourty, Malcolm Butler and Jerod Mayo since Freeny and Chung have to fight through blocks first.
After Osweiler tosses the ball to Anderson Jerod Mayo committs a mistake and gets sucked to the line of scrimmage from where he can no longer make a play while affording the Broncos numerical parity on the outside. Devin McCourty is getting blocked at the line of scrimmage while two Broncos have a free release at Freeny and Butler. From there all that stood between Anderson and the endzone was a missed tackle by safety Duron Harmon at the 30-yard line.