The Four Triangles

Football theory essay question:

A triangle read combines a vertical stretch to defeat Cover 2 with a horizontal stretch to defeat Cover 3, providing options regardless of the defensive coverage (many of these plays will also include crossing routes to defeat man coverage).  There are four possible ways to orient a right angle along the axes of a grid (|_, _|, |¯ , ¯|), so there are four possible ways to orient a triangle read.  But are all four of these triangles in use in football today?  Why or why not?

Triangle 1: Lower Outside Apex

This is the classic triangle read pass, used in plays like Mesh (Air Raid version and Coverdale & Robinson version), Stick, and Double Quick Outs.  The receiver in the flat does double duty: he is the low man in the high-low stretch on the cornerback that is a classic way to attack 2-Deep Zone, and he's also the outside man in the inside-out stretch on the outside linebacker or sky safety that is a staple of attacks on 3-Deep.

 Mesh, Coverdale and Robinson version

 Mesh, Air Raid version

 Y-Stick

 Double Outs

Triangle 2: Upper Inside Apex

This is the next-most common version, used in plays like Stem/Chair, Y-Cross, Boundary Corner, and the eponymous Triangle.  It attacks the seam, an area of weakness in 3-Deep zone, with a high-low stretch on an inside linebacker, a player whose zone drops are not usually his strongest trait.  The deep man in that stretch also serves to occupy the hash safety in 2-Deep zone, making it harder for him to help over the top with the deep route outside.

 Stem/Chair

 Triangle

 Barrier Corner

Y-Cross

Triangle 3: Upper Outside Apex

The weakness of 2-Deep zone is in the contain unit, where only two safeties have to cover the width of the field.  Putting two deep routes on the same side of the field stresses this unit to the breaking point, while a flat route outside prevents the cornerback from sinking to help outside.  So why is it so hard to think of an example of this Cover 2 killer?  A smash combination with a post is about the only thing that comes to mind.

Double Smash, Post

Triangle 4: Lower Inside Apex

Rotating the triangle so the apex is to the lower inside puts the horizontal stretch back on the flat defender, a classic technique for attacking the weak undercoverage of Cover 3.  Combining this with a route into the seam between the deep zones is a no-win situation for 3 Deep Zone and its derivatives. The hook zone linebacker has to either sink with the seam route, leaving the flat defender exposed in a two-on-one, or take the short inside route and allow a receiver to run free into the weak part of the secondary.  Yet this is not a common route combination in practice - certain incarnations of Shallow Cross maybe come close, but the main purpose of Shallow remains the three level vertical stretch down the middle of the field.

Shallow Cross

If Triangles 3 and 4 look like such devastating weapons against Cover 2 and Cover 3 respectively, why don't we see them in games and playbooks?  Because they are one-trick ponies.  If Triangle 3 is called but the defense lines up in Cover 3, all three routes will run directly into occupied zones.  Likewise, if Triangle 4 is used but the defense plays a 2 Deep, the defense will find receivers coming to them almost without moving.  Triangles 1 and 2 combine stretches that hurt both Cover 2 and Cover 3 (and usually also involve rubs to defeat man coverage), so the passer has options no matter what defense is called.  In fact, the passer doesn't even have to totally diagnose the defense on such plays, since just going through a progression should yield an open receiver.  This is a huge advantage against defenses that look similar but play very differently, such as Cover 2 and Cover 4, or against teams that roll from one look to another pre- or post-snap.  Triangles 3 and 4 just double up on stretches that attack the same defense.

Of course, lots of classic pass patterns only attack one defense.  Curl/Flat, 4 Verts, Slant/Shoot and All Curl are Cover 3 beaters.  Fade/Out and Smash are for Cover 2.  The difference between these plays and the triangle reads is that these are all two-man routes, allowing the remaining receivers to mirror the play backside, run a different combination as a packaged side, or provide extra blocking.  The offense has limited capital to work with, so if it's going to invest three of its five receivers in a pattern, it should be a pattern that works against as many coverages as possible.

So should offenses shy away from Triangles 3 and 4, outside the most obvious coverage situations?  No indeed.  The next step in the evolution of the triangle read is completing the square.  Adding a fourth receiver changes one triangle into all four.  Instead of guessing on the defense and trying to use Triangle 3 or 4, now both are in play at once, along with Triangles 1 and 2 to boot.

 Quad Read (Modified Mesh)

 Quad Read (Modified Y-Cross)

The two common triangles are common for a reason - their versatility gives options against any defense.  But the other two can be devastating against the right coverage, or with the addition of an extra apex.