I think almost every Jets fan appreciates how great Nick Mangold is. It sounds as though he will not play in tomorrow's game against Oakland. Dakota Dozier or Wesley Johnson will likely be a downgrade when it comes to blocking.
Mangold is not just as important as a blocker. Losing him means the Jets are going into a road game with an inexperienced center. A center needs to be one of the smartest players on the team. In many situations, he and the quarterback are working in tandem to make sure the blocking scheme is set up correctly on a given play. They set it up according to what they expect the defense to do. If you see Peyton Manning running around and pointing before the ball is snapped, he is probably setting up the blocking scheme.
One of the most important things to do before a play is figure out which player is the middle point on the defense. This is called identifying the MIKE linebacker. The most direct path to a quarterback is up the middle. This is why Todd Bowles frequently has his middle linebackers blitz after disguising his fronts. He wants to try and force a mistake, and with a middle blitzer, a mistake can mean catastrophe.
I am going to give a few examples. Forgive me as these are going to be overly simplistic in the name of clarity. Blocking schemes on the NFL level get much more complicated than this.
In this case, the Jets know the four pass rushers coming along the line. The question is which Patriot is the MIKE. Is it Patrick Chung (23), Jamie Collins (91), or Donta Hightower (54). Who is the center of the defense? Who is going to blitz up the middle?
In this case, it is Collins. Collins is Nick Mangold's man.
The Jets have two backs in to help. This is going to be a seven man protection. Tommy Bohanon is on the right side of the formation. He is going to be responsible for any additional blitzers coming from that side (most likely Hightower). His job is to start looking on the inside since once again, inside pressure will get to the quarterback quicker. Zac Stacy is responsible for the left side (most likely Chung), working inside out.
What happens if the Patriots send a fourth extra blitzer with only Mangold, Bohanon, and Stacy to block? That guy becomes Ryan Fitzpatrick's responsibility. He either has to figure out a way to elude that rusher or (more likely) get the ball out before that rusher gets to the quarterback. Ideally, a receiver will see this and the two, reading each other will be on the same page changing the route.
A situation like this is also why you will typically see extra blockers like Stacy and Bohanon take the inside guy. If you have a free runner, you want him to be as far outside as possible because he will have to travel a greater distance. This gives the offense a little extra time to operate before he gets to the quarterback.
On this play, the Jets have it right. Collins blitzes right up the middle. Mangold takes his man. Hightower blitzes from further away on the right side of the offense. Bohanon is able to pick him up eventually. Chung drops into coverage, and Stacy is free to release into a passing route.
The Jets handle this pressure well, and Fitzpatrick completes a pass to Brandon Marshall for 13 yards and a first down. You can imagine what would have happened had the Jets not set up their blocking correctly with blitzers firing up the middle.
Now let's take a look at what happens when the blocking is set up incorrectly. We will go back to London. You might remember the series before the half when Buster Skrine blitzed out of the slot three straight times successfully. We are going to go to the second down play. Skrine had just hit Ryan Tannehill on first down.
You can see right here that Mike Pouncey is pointing at Demario Davis. The Dolphins are declaring him the MIKE.
Now take a look at what happens. Since the Dolphins have declared Davis as the middle man on the defense, Pouncey is blocking him (square). What really happened, though? See the Jets have rushed five. The middle man is actually David Harris (triangle). Buster Skrine is coming free off the edge (circle). The Jets rushed five. The Dolphins have five blockers. One Jets rusher is heading to the quarterback unblocked, however, because the protection is set up incorrectly. (Something, something $77 million franchise quarterback.)
Replacing a guy like Mangold with a player lacking experience is going to be a bit of a hit. Without knowing the exact inner workings of how the Jets run things, there usually is some sort of collaboration between the center and the quarterback in setting these things. More of the burden to correctly identify what the defense is doing will likely fall on Ryan Fitzpatrick's plate now. This is an area where it might help to some extent having a experienced veteran in Fitzpatrick starting than say Geno Smith or Bryce Petty.
Hopefully Nick gets better soon, though. He does a lot more than people realize.