Inside the Playbook: Purdue's Weakside Flood and the QB Keep Concept

Purdue is a “concept” team; by this I mean they have a few dozen concepts (give or take) and they build an entire offense off of this. In many ways, this is a very effective way to build a simplified offense that can be executed at a high level; you combine individual concepts and your playbook can grow into the hundreds, but your players only need to learn their few dozen concepts (which includes run concepts). You’ve simplified the game for everyone: OL and QB, and maybe most importantly, for your QBs and WRs. Because what they learn is limited, they can learn it in more detail, meaning they understand the nuances and adjustments that can be made on the fly. The QBs and WRs get more reps running only a handful of plays, and they understand each other’s reads and in-play modifications.

One of the concepts I want to take a closer look at is the Weakside Flood.

Weakside Flood
As I said, one of these concepts that Purdue runs is the Weakside Flood (often referred to as the QB Naked or QB Keep concept). This concept provides a high/low read on the CB and an in/out read on the hook/curl defender; this is also known as a triangle read. Run to the weakside of the formation, typically there are fewer defenders to cover the space that is being exploited because they need defensive numbers on the strongside to account for the run threat. On top of that, this concept is often paired with a play action fake; the routes coming from the opposite side of the field act as down blocks from TEs or WRs, making the play fit well that scheme.

Green Square = 1st Key
Blue Square = 2nd Key

Corner Route
Purdue likes to sell the corner route initially stemming inside; it works to about 3-5 yards from the hash, and then gets vertical, before breaking back to the corner at 10 yards depth. This does a few things for the offense. First, this helps sell the PA a bit (cutting off the corner or working to the safety), but also attracts the attention of the safety and helps define the CB’s coverage. By attracting the safeties attention, you prevent him from cheating down as much; you also construct a sort of wall for the flat receiver to run under and pick off any in-to-out coverage. As far as defining the CB’s coverage, when the receiver stems inside, the CB will typically either follow or let him go. If he follows, the read is obvious for the QB. If he lets him go, the QB can tell if the CB is retreating (opens his hips inside and retreats into a deep third) or squats (stays flat footed with a forward lean). This will help the QB, as we’ll discuss in the progression section.

Shallow Cross
The TE will always want to release inside unless there is a 7-tech defender. He can work under the 2nd level of the defense initially but he wants to eventually work 5-6 yards depth by the time he reaches the OT on the opposite side. At this point, he can start looking back to the QB for the ball. He keeps working under control toward the sideline while looking back for the ball, the QB will throw the TE open (either throw to his current location to stop him, or lead him) when the throwing window opens up.

Intermediate Cross
The receiver will always release inside, unless it is a TE and there is a 7-technique defender. He needs to be behind the opposite side 2ndlevel defender, and he’ll work to 10-16 yards (depending on initial split and level of the hook/curl defense). Typically, the initial stem will work at about 45 degrees for the first 5-7 yards, the route will then adjust to threaten the middle of the field for another 5-7 yards, before breaking back to the sideline, gaining the additional depth by the time the formation is crossed, looking back for the ball by the time you reach the far hash. We’ll come back to this “far hash” concept a bit toward the end of the article.

The first movement key is going to be the defender over/outside the outside receiver, typically a CB. If the CB sinks with the WR (runs with him or gains depth), the movement key is the hook/curl defender that is being picked on with the threat in the flat and an intermediate threat on the hash. 

CB Drops, WILL Stays Inside

CB Drops, Will Gets Outside

Note that I say the Hook/Curl defender, which could be the weakside LB or the safety from deep; it will change and the QB will have to identify that second movement key. Particularly with the PA fake pulling the WILL out of the play, it is often the deep safety trying to rob that shallow cross.

CB Sinks, FS Robs Down

On the flip side, if the CB stays flat footed and stays shallow, the QB’s next movement key will work inside to the safety, where the corner route and the intermediate cross will work as an inside/out threat on him.

CB Sits, FS Cuts Cross

CB Sits, FS Runs Over Top

It is essential that QBs are extremely comfortable with these reads and get the ball out of their hands. In this concept, being on time with the throw is key for the success of the play. Because you are flooding one side of the field and typically rolling in that direction, the field gets condensed. This helps the QB’s reads, but it also allows the defense to play in a smaller space if they are allowed to react. Therefore, the ball has to come out as soon as the movement keys are established, and the QB must be able to read and move to the 2nd movement key quickly.

Example 1
Purdue lines up in a Trey formation (TE and two WRs to one side; split end on the opposite; also known as “Far Trips Left” in WCO lingo) to the field, with the RB aligned in a far position. WMU is in a 4-3 Under with a Loose SAM, showing a 2-high defense.

At the snap you see the QB give an outside zone play fake as the OL starts their slide protection; the X-WR is already stemming inside with his eyes on the deep safety and the Y-TE is beginning his cross with his eyes on the far LB. You also see the Z-WR begin his intermediate cross working directly inside.

The QB pulls the ball and begins his naked roll to the right. You see in the next image that the CB is retreating, his eyes on the X-WR. Immediately, this is a key to take his eyes inside. Seeing no one crashing down, he immediately makes the throw, not wasting any time.

Both the safety and the sinking CB are attracted to the banana route, the intermediate cross hasn’t even come close to completing his route, and the ball is already out of the QB’s hands as soon as the throwing window opens up.

And this results in a TD

Example 2
Same formation, just flipped as Purdue is now on the left hash. WMU is showing a slightly different formation, a standard 4-3 Under with the SS flexed over the slot.

The mesh point sucks up the defense as the receivers begin their routes. The TE works to the 2nd level and clobbers the MIKE for half a beat before releasing.

The CB is again clearly following the X-WR in but with safety help over the top, and as soon as the QB sees the CB dropping, he ends his 6 step half roll, takes his eyes inside to check the second key, and then simply waits for the window to open.

Window comes open, and it’s a TD.

Example 3
Now let’s take a look at one that doesn’t just attack the flat. Purdue lines up in an I-Formation with a TE and Wing to the field and a single split-end to the boundary (In WCO lingo: Green Left Tight Zoom), but we’re running the same play.

A bit different protection scheme here, as Purdue pulls the backside OG to sell fully sell Power O to the strong side (the FB also looks to cut the DE).

The X-WR begins his banana route with the stem inside toward the hash, Y-TE begins his shallow cross after selling the run, and the wing starts gaining depth for his intermediate cross.

The CB follows the X-WR, but as the QB gets his eyes inside, he notices the weakside safety jumping the shallow cross; his progression should take him to the intermediate cross then.

The QB either doesn’t find him or finds him too late (which would lead him into the FS looking to jump the route). If he gets through his reads on time, he hits the intermediate cross for a nice gain, but with the delay, he can’t. He eventually throws into one-on-one coverage deep to the corner route, which isn’t a bad choice, and the WR makes a spectacular catch for a TD.

Same Concept, Different Look
Now here’s where this Keep concept becomes really interesting. We’re sticking with the same basic concept in that, in general, there will be receivers running to the same three spots, off of play action, and the QB will make the same exact reads, but different personnel can run the variety of routes.

Example 1

Here, Purdue has a close Stack to the boundary, a wing to the field, and an X-WR split wide on the far hash. A single RB is lined up directly behind the under-center QB.

The OL hard slides left as the QB bluffs a handoff to the right. The wing down blocks on the DE to hold him there. The X-WR to the field begins his corner route with an inside stem. On the backside, the on WR in the stack a deep route to hold the safety while the off receiver runs his intermediate cross (not that the off WR starts slightly outside the up receiver, this stack will often lock the outside CB to this receiver, and the stack will serve as a rub as the two receiver switch positions with their stem). Lastly, note the RB is only running a weak fake as he looks to get out to the flat quickly.

That’s right, the RB is running the flat route, just as a TE would run the shallow cross. Everything else is the same: the X-WR runs a corner route and an intermediate cross comes from the opposite side. The QB’s reads are also the same. This means pretty much everything for the offense is the same, but it’s a new look for the defense. The wing’s down block on the DE is enough to sell the run to the defense. As the QB sees the CB following the X-WR in coverage, his eyes can immediately go inside and see that the PA was enough to hold the OLB just long enough for the RB to slip into the flat. He throws it just as the RB gets back to the LOS.

Here's pretty much what it looks like.

And it turns into a really nice gain.

Example 2
Purdue is again in a single back formation, with a TE and wing to the boundary and a stack to the field, aligned close to the formation. SIU has three deep across the back with a bracket coverage over the stack.

Here, there is no play action and both TEs stay in to block. The RB runs out on a swing route (the flat threat), the outside WR runs his corner route, and the underneath receiver stems to the field hash before threatening vertical and sitting at depth right on the hash.

What you can see in the previous picture though is that the CB is flat footed and square to the Z-WR running his hitch. The QB sees this immediately, as the bracket coverage isn’t very well defined. But this is part of the great part about this play design. The stack incourages bracket coverage; the outside receiver stems inside and the inside receiver stems outside, but it is the outside receiver that will run the corner route and the inside receiver that will run the inward breaking route. In other words, the route stems are set up to attack away from the coverage. By the time the X-WR get to his outward break, the QB has made his read and is ready to make the throw. The CB is stuck sitting on the underneath routes and the safety is held inside, so the corner route can get easy separation.

Here's what it looks like.

And this is a fairly easy TD throw with the CB sitting underneath.

Example 3
Oh, but it’s also our favorite West Coast Offense staple: Spider 2 Y Banana. And you can run this play in multiple ways.

How about with the RB as the flat threat (with the FB cutting the DE), playside TE as the corner route, and farside TE as intermediate cross.

How about an unbalanced line, with the FB as the flat threat, the playside TE as the corner route and the backside wing as the intermediate cross.


From more of a spread formation, you betchya:


What about a Yogi concept? Yup, it’s pretty much the same thing.



The point being, you can throw a ton of looks at a defense and keep things simple for your QBs and receivers. That’s what being a “concept” offense means. This concept is essentially this: a playside receiver is running a route to the corner (many coaches will coach this as an “Alert” throw, only peek to it before moving on); receiver will come from the formation – either playside, far side, or the backfield – and run a short route toward the sideline; a third receiver will threaten behind the flat route at an intermediate distance. Combined, these three routes will form a triangle, in which the QB makes the same read every time.