The last couple days, Les Bowen has published some good quotes from the linemen about why the Eagles' fourth down attempt failed against the Vikings. From Jason Kelce:
"[W]e started with a combination block between me and [left guard Evan Mathis]. The 'backers were flowing hard to their gaps, so you can't stay on the double-team very long. When he left, I started pushing my guy to the left, and Shady tried to hit that hole. It looked like he just dove forward.
And Jason Peters:
"It just came down to technique, hat placement. They loaded the box, but you know, 1 yard, it don't matter what they do, we should be able to get it. We watched the tape today. It was all about hat placement, being in the right spot, staying in the double team a little bit longer . . . Little bitty things that we've just got to clear up this week."
And indeed, if you watch the play, that's what happened. Mathis and Kelce initially have the double team, but once Mathis comes off for the diving linebacker, Kelce can't quite keep his man out of the hole:
What struck me about the play, however, is just how tight the tolerances are. For Mathis, you're talking about a "come off" zone that's maybe half a second long. If he leaves too early, you get the above result. But if he's too late, then the linebacker shoots through unmolested.
One possible adjustment -- and I guess it's the one I sort of expect -- is for Peters to bluff a block on the defensive end and then go for the linebacker instead. You're making the calculation that a guy standing that far outside won't be able to stop Shady before he gets 12 inches.
But a later short-yardage play from the Vikings demonstrated another possibility:
It's not exactly the same setup, but again you have a team not needing very much yardage and a linebacker crashing into the hole they want to run through. But in this case Minnesota solves that problem by accounting for DeMeco Ryans with the fullback.
Lead blockers are basically wild cards. They can go whichever direction the runner does, meaning the defense needs two players rather than just one in that gap.
I descend into self-parody when I talk about putting James Casey on the field more, but it seems like this is exactly the role he can be asked to play on this team. Third-string tight end most of the time, sure, but occasional fullback in high-leverage situations.
Kelly's already running more of the offense under center. Could we see the I-formation next?