Ben Muth said:
If you look at the picture above, you see there’s already a huge hole developing. Byrd has a great view of the play as it is developing and has the best chance to stop it.
It’s Byrd’s job to come in and squeeze that hole as much as possible while keeping his outside arm free to make a tackle if Brandon Bolden bounces it outside Gronkowski’s block.
This is not to correct Muth, as the way he describes it appears to jive with Byrd's responsibilities as he plays them here, and its more of a FYI, but there is another method front seven players, as Byrd is here, or even force players, use against trap and counter blocking such as this, and its called Wrong Arm technique.
Instead of keeping his outside arm free and trying to fend off a kickout block with his inside, which is admittedly ideal if difficult, Wrong Arm means meeting that trap blocker (Gronkowski) with the outside shoulder in front, i.e. hitting him with the "wrong arm" from a tackling perspective... basically you are turning into him with force, and the idea is to blow up the blocker as quickly as possible without worrying about making a tackle or defending your gap. If you blow up the block fast enough or hard enough, the running back can't use it as a lead and has to cut around the pile, both of which delay him getting upfield.
This is sometimes called "trapping the trap." You are essentially defensively trap blocking a trap blocker.
If Byrd or the Bills had used Wrong Arm here, it is probable that Bolden would have had to bounce outside, which would have given the safety a better angle on him, allowed the cornerback to get involved, and given any other defenders in the area a longer opportunity to get off blocks. Bolden ended up tunneling right up the middle of the field for 20 yards.
