Wednesday, October 19, 2011

49ers vs Lions; Gore's big runs

Today I promised to take a look at Frank Gore's two big runs of 47 and 55 yards from Sunday's game against the Lions, mainly because both runs came using roughly the same play call. Now I've since discovered this play was actually covered by Chris Smart on his site, Or more specifically, he covered it for and obviously left a link on his own site.

On this note I was about to abandon my plans on the principle of redundancy, until I noticed something about the write up that caught my eye, that being that the blocking scheme was actually drawn up wrong from the right guard leftwards. I should point out that this is very much unlike Mr. Smart, whose blog is normally one of the true gems of football blogging. But I wont complain, mainly because it gives me something to do by drawing it up.

We'll look at the 47 yard run to start with. The video clip of the play is here on First things first, lets look at the starting positions, pre-snap;

Before we get down to the detail, we need to point out some issues. The first thing an astute observer will notice is that the wide receiver on the left side is missing, as is the corner covering him. That's basically because they're not of great importance to this play. The other thing we have to be wary of is that there were no decent camera angles (all the more reason to switch to Skycam during games) so the position of the linebackers and and safeties may not be perfect. I did the best I could using the hash marks as a guide.

You'll also notice that the defensive end on the right hand side (from our perspective) is quite wide. This is because the tight end was split out a little and the end lined up on his outside shoulder. This is a good example of the fabled "wide nine" that the Eagles have been using and ironically enough - given the reason that I'm doing this - was covered by Chris Smart in his most recent post.

So now we've laid the ground work, just what is all the fuss about this run? Well as Mr. Smart pointed out, there are two tight ends on the field. One is Vernon Davis, who is split out to the right and has the defensive end lined up on his shoulder.The second is Delanie Walker, who is probably the most under rated asset on the 49ers offense. He's lined up behind Davis and is going to go in motion slightly towards the formation and then do something incredible. Kind of.

The 6 foot tall, 242 pound Walker is going to be asked to block the 6 foot 4 inch, 307 pound Ndamukong Suh.... Believe it.

So how does a tight end, known more for his receiving, manage to block a defensive tackle with a reputation for tough, physical play, and who out weighs him by 65 pounds? The answer is to use a bit of finesse and a bit of trickery; by giving Suh a sniff of an easy tackle for loss, and by putting the tight end in a position where he can block down on Suh from an angle, giving him an advantage in leverage while not asking him to knock Suh clean off the ball, just pin him inside for a moment.

(I should clarify at this point that the "N" in the diagram above means "Nose" not "Ndamukong". Suh is actually the "T" defensive tackle. I only just realised that this might cause confusion and, well, frankly it's easier to type this explanation than it is to go back and change the diagram!)

This is known as trap. You're giving the defensive linemen the impression that he has a free shot into the backfield, only to blindside him with another blocker. Not only is this an effective block on the play being run, but it also serves up a minor side effect of interest. In the future if that defensive linemen finds himself running free into the backfield (perhaps due to an assignment error by the offensive line) there's a chance he will hesitate for a moment and take a quick peek to the side, worried about getting trapped again. We sometimes see this same effect in defensive linemen when they play against a team that runs a lot of screen passes to backs.

Now, up to this point Chris Smart had the scheme down pat. But what he missed was what was happening from the right guard onwards. He wrote that the interior linemen went up to get the linebackers but that's actually not what happens. In fact both the right guard and the left guard are going to perform trap blocks themselves. The left guard, first rounder Mike Iupati (rookie watchlist from last year) is going to pull off the line and go left to get the wide defensive end on his side. The right guard, Adam Snyder, is going to pull off the line and go left to trap the other defensive tackle.

This does three things, all of which are important. Number one, it frees up the center and left tackle to go and get two of the linebackers. Number two, it draws the linebackers to move left (from our perspective), because they think they're seeing a power run to that side. This makes them easier to block for the offensive line. Number three, it draws the weak safety down and to the left for the same reason as the linebackers (he thinks he sees "power"), and this draws him away from the true path of the running back. Remember reasons two and three, we'll touch on them again later.

At this point I think it would be helpful to put up a visualisation to ease our understanding of what is taking place;

There we go. Now you can see all the blocking assignments for the offense, with the exception of the wide receiver off to the left, who would ignore the corner on his side in favour of coming inside and cracking down on the weak safety. The dotted line coming from Delanie Walker indicates his pre-snap motion, triggered by a small foot movement by quarterback Alex Smith. Walker shuffles across to get behind the right tackle, then after the snap he turns inward and slams into the side of Suh, trying to pin him inwards.

The only person left unblocked (and who has a realistic chance of actually making the play) is the strong safety Amari Spievey, who you can see lurking in the top right corner of the diagram. The play is run pretty much right at him and he comes flying downhill to fill the resulting gap and attempt the tackle. The trouble is he's counting on everyone else to fill the other gaps and unfortunately the "Sam" linebacker Bobby Carpenter (whose being blocked by 49ers right tackle Anthony Davis) ends up out of position. The ironic thing about that is that Carpenter actually does a great job of beating the block by Davis, chucking him to the side, but goes the wrong way. He goes into the gap already being filled by Spievey, leaving Gore with the opportunity to cut back to the inside and use Anthony Davis as a barrier.

Here I've drawn the play out with the approximate positions that everyone ends up in, also showing the path that Gore takes;

As you can see, Gore knifes right through the heart of the Lions D and will eventually be brought down near the Lions goal line for a 47 yard gain. Chris Houston, the corner on the right side (from our perspective) is the one who chases Gore down and makes the tackle, after 49ers receiver Ted Ginn jr. fails to make any contact with him at all, merely herding him away from the main effort of the play.

The second time the 49ers ran it, they got an even bigger gain of 55 yards. Video here for the interested. The blocking scheme works out slightly differently this time around, mainly due to the reaction of the defense. In this second run, the defensive end to the playside identifies the play and comes inside the tight end. The wide receiver to the playside cracks down on the "Sam" linebacker (who has in fact been replaced by Lions Nickel corner Eric Wright). The right tackle goes up and finds himself blocking the same man as the center. Luckily the tackle realises his mistake and comes off in time to block the strong safety.

In the end Gore cuts outside around the rushing end, then back inside of the wide receivers block on Wright, then back to the outside to get past the safety. Corner Chris Houston is on the field again, but he comes down far too wide and Gore is able to get inside of him and up the field. Houston ends up chasing the play down from behind and again making the tackle, which probably highlights the main flaw that Frank Gore has; his lack of speed in the open field.

Now before we wrap this up, do you remember earlier that I mentioned the pulling action of the guards drawing the linebackers and the weak safety across to the backside of the play? No? Well go back and read it again, because I did.

The reason why this happens is because the pulling action of the guards in that manner looks a lot like the action that happens when both guards pull for a "Power" play. The difference is that on the Power play the Guards would be lead blocking for the running back, whereas here the guards are going away from the running back. That adds another dimension to this play for the offense, as not only is it a good play in isolation, but it also serves as a compliment to the Power play, showing the defense one action but giving them two very different plays.

Which leads us nicely back to where we began, with Chris Smart, and an article he wrote in 2008 about the constraint theory of offense.

So that's your lot for today. Thanks for stopping bye and hopefully you'll spread the word about the blog. Tomorrow I'll follow up my post from last week about the "Outside Zone" running play by going over its sibling; the Inside Zone.

Till then, enjoy your day.

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