Inside the Play: Iso Weak

Perhaps the most used play in the Tennessee Volunteers offense is the inside zone. The Vols are a run first offense, and inside zone is a perfect physical, downhill running play that fits what the Vols are trying to do. Defenses have many ways to attack inside zone, and one way that they do that is to read the offensive line’s blocks and flow aggressively to the playside. When a defense is aggressive in flowing to the playside, something Butch Jones likes to go to is a concept called Iso Weak.

To keep it simple, inside zone is built around the offensive linemen all moving in the same direction, creating double teams on the defensive tackles, and working up to the linebacker. The back reads the blocks and looks for a crease in the defense. For more on the inside zone scheme, check out this post (If you’ve never read it before, I highly recommend clicking the link and reading this post before you continue with the current article. It helps explain Inside Zone, making it easier to understand why Iso Weak works.). Iso Weak looks very similar to inside zone, but one distinct difference in the blocking scheme makes it a totally different play.

Iso Weak is very similar to Split Zone. The split zone concept is a nice compliment to inside zone. Split zone calls for the tight end to line up on the play side and cross the formation to execute a “slice” block on the backside defensive end . The linemen block for inside zone. This is a play Tennessee runs all the time.

Split Zone

From a blocking standpoint, Iso Weak is almost exactly the same. The key difference is that the backside tackle and tight end exchange responsibilities. The tackle will kick out the backside end and the tight end will pull through to the backside linebacker.

Iso Weak

The blocking looks like inside zone, but this is a designed cutback. In this example, the linemen moving to the right should get the defenders thinking that it is just another inside zone run to the right. But instead, the back will cut back left and follow the tight end as his lead blocker through the hole.

The name “Iso” comes from the word isolation. The design of the play is to isolate the tight end and the backside linebacker, one-on-one, in the running lane. The tight end is the lead blocker and must make his block in space to open up the run.

Offensive coordinator Mike DeBord went to Iso Weak on the Vols very first offensive snap versus Arkansas, and Jalen Hurd turned it into a big run.

Right off the bat, we see a few important things. First, the offensive line is moving right, showing inside zone. The left tackle Kyler Kerbyson blocks back on the defensive end and Ethan Wolf, the tight end, pulls through to make the lead block on the linebacker.

Iso Weak 1.1

In this case, the defensive end actually fights inside, so Kerbyson has to change his angle. Hurd is able to read the block and bounces outside, eventually gaining 35 yards on the play. The Razorback defenders flowed with the blocks, and the outside was wide open. While the play is designed to be run behind the tight end, Hurd has the authority to read the blocks and make his cut, and here he does an excellent job of finding open space.

Iso Weak 1.2

This is not a new play to the offense, as the Vols ran Iso Weak often in 2014. Most notably, the play was run in the Taxslayer Bowl, and Hurd ended up in the end zone after one attempt.

At the snap, we can see that the line is doing a fantastic job. The right side of the line was able to get very good movement at the point of attack. With Kerbyson’s block on the end, there is a big lane for Hurd. Wolf just has to make his block on the linebacker.

Iso Weak 2.1

Wolf executed perfectly and Hurd was able to explode through the designed rushing lane. 29 yards later, he’s in the end zone. This is exactly what the Vols want: A powerful run up the middle with the tight end making a key block and Hurd following him through the hole.

To summarize, Iso Weak is a really effective play for the Vols. For a team that uses inside zone as much as Tennessee does, Iso Weak works really well because it gets the defense flowing one way, while the play is designed to cut back in the opposite direction. Ethan Wolf specializes on this play, as he gets to be the lead blocker and get to make a big block, one-on-one, with the linebacker. Wolf is a athletic player who can get to the right spot and his strength and technique serves him well when making his block. Iso Weak will never be a featured play, but it is a nice counter and surely will be seen going forward.


4 thoughts on “Inside the Play: Iso Weak

  1. Thanks for the analysis — I’ll be watching for this against Georgia.

    I wonder if this could work if the weak side tackle went and blocked Will, while the TE smashed the End (which is his assignment on the split zone). At least this way, our weak side tackle’s assignment doesn’t become a key for the free safety.

    Just wondering. I’m still learning X’s & O’s, but I do understand strategy pretty well from my chess playing days.


    1. Thanks for commenting, Chuck.

      Some teams do run split zone and teach a designed cutback, so it looks like what you are describing. But for the Vols, iso weak is a designed cutback, while split zone is run just like a regular inside zone play.

      A designed cutback for split zone is equally effective because, as we see with iso weak, there is often a rushing lane in between the backside end and linebacker when the tight end crosses the formation to block.

      Even when the Vols run split zone, often the backside opens up, and Hurd can read the blocks and make the cut. Hurd has the freedom to find the best hole to run through on any of the zone plays. On iso weak, they really want him to follow the lead blocker, unless the outside is just wide open like it was in the first video clip.


  2. Excellent article! Thank you!

    As the play is called Iso *Weak* I can see it’s been designed to be run to the 1-tech side. Any ideas what might happen if the play is called and the defense lines up in a way where there’s a 3-tech where a 1-tech was supposed to be? Is there a way to run this to the 3-tech side, or do they just audible out of it?

    I know it might be guesswork but any ideas are appreciated 🙂 Thanks again for the article.


    1. My guess would be they would check to Split Zone vs a 3 tech and Iso Weak vs a 1 Tech. Because the hope on Iso Weak is really to hit the B gap, and it’s going to be hard to do that with a 3 tech. But that’s just a guess.

      Thanks for reading.


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