The Patriots run defense undoubtedly struggled against the Jets- and it's a struggle that's reared its head against the Dolphins in week 1 and the Chiefs in week 2. Through seven games, he team has allowed the 5th most rushing yards in the Bill Belichick era, along with the third worst yards per carry allowed.
The three games with 190+ rushing yards allowed are the most allowed through seven games under Belichick- and 2002 (the worst year) only had four the entire season.
The defense will need to step up its level of performance as teams would absolutely love to run the ball.
Similar to how the Chargers competed with the Broncos last season, the idea is that a team who can run the ball well and control the clock can prevent a high flying offense, like the Patriots, from racking up points. By controlling the time of possession, the Patriots won't be able to develop a rhythm or create a game defining lead. The Jets nearly pulled it off.
The loss of Jerod Mayo cannot be understated. It has forced the Patriots adjust and play in a 4-2-5 front, instead of a three linebacker package. This both weakens the defense by putting lighter players on the field, but also forces sophomore Jamie Collins to slide inside where's he's obviously less comfortable.
Upon film review, it's clear that the issue is not the scheme of 3-4 versus 4-3, or a matter of defensive line personnel. Unlike week 1, where the Patriots played Chandler Jones at 3-4 defensive end for a reason still unbeknownst to the world, the Patriots defensive line played well enough (apart from a handful of plays) to succeed. The issue came with the clean-up crew.
The idea behind the Patriots 3-4 front is that the defensive linemen will eat up space to allow the linebackers to crash the gaps and make the tackles. Jerod Mayo has an uncanny sense of knowing where the hole will be and can generally clog it as soon as it appears. Generally, the linebackers will have one of two lanes under their watch and they just have to choose correctly to make the play.
The idea behind the Patriots 4-3 front is more of a single gap approach; the defensive ends set the edge, while the defensive tackles man up in the middle- or even let Vince Wilfork two gap. The idea for the linebackers is that they just have to attack whatever offensive lineman is open to prevent them from getting to the second level; no one was better at this than Brandon Spikes. But generally, the offensive line will try and create a running lane with the free lineman so the linebacker needs to be able to attack the lane.
Here you see the Jets pull their left guard to try and open a lane against the Patriots front. Vince Wilfork is one defensive tackle, in front of 66 and getting triple (!!) teamed. Casey Walker is getting sealed by the left tackle and the center. The lane behind the Jets center and their pulling left guard is the obvious lane for running back Chris Ivory.
In this case, veteran linebacker Dont'a Hightower shows his savvy by attacking the hole and forcing Ivory to bounce back inside. Hightower makes the play, but his awareness to clog the lane both forced Ivory away from the Jets planned running lane and put Ivory in a position where any number of Patriots defenders could make the play.
Also, let's treasure the fact that the Jets triple teamed Vince Wilfork and he didn't move.
The following play is what not to do.
The Jets part the Patriots defensive line line the red sea and a gigantic running lane appears for Ivory. Hightower attacks the open guard to prevent them from getting to the second level, but the danger of having just two linebackers is that now Ivory has a cutback lane and there's no one there for clean-up.
You can see Collins, who had a chance to attack the hole, looking hesitant about where he should go. He has to think about what to do; he's not reacting quickly. Instead of Collins crashing the cutback lane, Jets tight end Zach Sudfeld (44) engages Collins five yards beyond the line of scrimmage and allows Ivory to have more space to run.
Collins ultimately makes the tackle, but not until after Ivory makes a large gain. Yes, the defensive line could have played better in this situation, but Collins inability to attack the ball carrier shows how much further he has to go for the game to start slowing down for him.
The sophomore is better fit to play on the edge, but so long as he's in the middle of the field he'll have to develop a degree of comfort crashing into the running lanes. Of course, another option would be to play rookie Deontae Skinner at middle linebacker to put Collins back into his comfort zone on the outside.
This is a decision for the coaching staff. But it seems that issues against the run no longer fall on the coaches performance, like they did earlier in the year; now it's a matter of the defensive players doing their job.