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Inside the Clemson offense: The Iso

Also known as the greatest play in football.

Why? Because its simple. Its the 2nd play that is taught to kids learning football after the FB Dive. So then it stands to reason if its simple, its also one of the easiest to execute. I make no secret that I love I-formation running, and with a good FB and decent power RB, this play should be good for 3-4 yards on every touch.

Clemson almost never ran this play in the traditional form with Spence, although he would run it out of a Strong-I and with zone blocking. This season Napier and Swinney have brought it back, given their success in college running it at Alabama and Furman.

The I-formation is so successful, since the 1950s, because its very balanced in how it attacks. The single wing was phased out of football when the T-formation came into prominence under George Halas and the Chicago Bears in the 1940s. Later,  Tom Nugent at VMI changed the T-formation into the I-formation, and then John McKay used it successfully at USC to win national championships, and then the NFL took it and distilled it into the style we see today. But the reason why its so successful is not that its a power-formation, other 2-1-2 formations can be equally as tough to defend, its in how it can still be effective in the passing game. If it were not, the NFL would not still be using it as extensively as it is today. Both backs can be useful as receivers, or can stay in for max-protection with the TE if need be, giving you a possible total of 8 blockers. Since many teams release one or both backs from blocking, the defense must defend the flats. Teams that have a shortage of competent WRs, but that have a TE that can block or catch, along with a good blocking FB, can excel at any level with the I-formation.

Theres so much more to write about the I-formation that it has filled many books, when all we want to do is discuss the play Clemson has run considerably more this year and more effectively than perhaps since Tommy West's days.

Why is it called the ISO? Its simple, the FB is isolated on a Linebacker or SS with a one-on-one block, leading the RB, who then cuts to either side of the blocker. It is sometimes called a "blast" play, but I have always heard that referred to more as an outside Iso. Its not designed to break long runs, because youre basically going right into the meat of the defense between the tackles. Its goal is consistent 3-4 yard runs, and by the 4th quarter, those will start to be 7-10 yard chunks. Either the offense will move right down the field and eat clock, or they will have to bring their safeties into the box, at which point the Sprint Draw/PA plays can kill them (indeed a sprint draw is basically a slow Iso).


The OL take the men in front of them for the most part, straight up man/man (base) blocking. The Tackles take the Ends, the Guard takes the 3-tech, the other Guard and Center take the Shade/NT. If the Center can handle him, then the Guard takes the MLB or a shifted OLB. If the Guard is covered with the Center free, he attacks the backside LB. Its called a man scheme and some call it a gap scheme, as opposed to a zone scheme that we run our single-back run plays with:

Gap On Down (GOD)- This is an off-tackle/trap scheme (usually) and it says that the playside blocker looks for his block to his inside gap. If there is no one inside the gap he checks for a defender directly over (ON) him. If there is no one inside or over him on the line of scrimmage then he blocks down on any man head up on the next offensive line man that's inside of him.

So for example, say the play is I-right 36 Iso. I-right means that the TE is on the right side, 36 means the 3-back takes it up the 6-hole (off the RTs hip). The right side is the playside. The RT looks to the guy inside, say the 3-tech DT, and if he's not there, he takes the DE right over him. If neither is there on the LOS, then he down blocks on the guy to his inside. Down blocks mean that you push the DLman towards the Center. Since he looks ahead and to his inside, there could be an OLB/SS sitting there off his hip that gets unblocked. Thats where the FB comes in. 

Gap On Man (GOM) - A slight change, and the 3rd step is if there is no defender in the gap or lined up over you then you block the 1st MAN (defender) in front of you. This is usually a linebacker. This is probably the simplest scheme that is taught to kids.

Thats just two possible schemes that are used, there are more, and we could go over them later. The goal is to keep it simple and fire off the ball....put a hat on a hat and drive him.

Depending on the hole the play is designed to take, the FB will start from 4.5 yards depth and aim at the hip or inside/outside leg of a offensive lineman, then take the first man he sees and drive him, which should be a linebacker if the lineman has held his block.

WRs stalk block their Corners, and the backside WR can be told to crack the Free Safety.

The QB gives the ball as deep as possible.

The RB takes a slide step then follows his blocker into the designated hole, this is the key difference between zone runs and this play, zone runs may have a numbered hole, but the back runs to an area then cuts. Zone plays have more cutback opportunities. From John McKay

We ask our backs to key the first defensive lineman to the onside. As they approach the hole, they will run away from the direction of the slanting lineman. If he slants in, its obvious the LB is going outside. Our tackle will just block the DT the way he wants to go, and our FB will "kick out" the LB who wants to go outside. If the tailback stays away from the FB, theres an alley for him to run through.

-Football Coaching Strategies

The problem with the Iso is that its a little slow to develop, and your linemen must hold their blocks. That means the Linebackers have time to react to the play and can shoot the gaps if your line cannot block. In the past, the combat was to give it to the FB. Nowadays, the FB rarely takes the Dive from the I-formation, and most FBs are blockers only. I haven't seen the FB Dive much since Nebraska fired Frank Solich. Chad Diehl doesnt get many carries on the Dive, but I wish it would come back because I think it will be successful.

Also, its not easy to put in misdirection plays and the LBs can hold their keys (the guys they watch) on every play. It doesnt have as much success running outside as inside. McKay's comment above applies to gap-control defenses like the gap-air-mirror (think BC, Wake Forest).

What problems would you have with the I-formation running game, and why doesnt Clemson run it all the time?With our zone blocking schemes in the Ace/H-back sets, you have the opportunity to combo block (double team) somebody on every play at the LOS before releasing. Thats how the zone run game works, or how its supposed to work.

In a man scheme like this play is generally run from, they wouldnt necessarily combo block, they'd just release to the 2nd level and hit a scraping backer if they are uncovered. So when you have McClain, who sometimes cant block a soul, on a 3-Tech DT, without any help from Cloy or Walker/Lambert, you end up with a DT in the backfield. Diehl has to chip the DT instead of a SS or OLB, who will then make the tackle.

I should add that most of our success with the I earlier in the season is the HB Power play, and most of it has come with CJ making the cutback to the left side of the line, when the play is designed to go off-tackle to the right. He rarely takes it up the 6-hole (between the RT-TE) as its designed.

If you want to run I-formation, youll end up with more 1-1 blocks than any offense in football, then you need good guys inside to move those DTs off the ball. Then the FB and any free Guard or Center can get to the 2nd level and open some big holes.

Now you can run zone blocking in the I-formation as well, the pros do it. You can also adjust the scheme to help McClain, and I would do that.