Ever since Dana Holgorsen and Oklahoma St put the diamond formation on the map in 2010, it's been a big part of college football with teams at every level of football putting it to use for a variety of different tasks.
Originally, Holgorsen was at a staff retreat with OSU staff, including current Texas OL coach Joe Wickline, and collaborated with Wickline to create the formation in a moment of boredom.
Oklahoma St brought Holgorsen for his expertise with creating explosive offenses out of 4/5 WR formations that flung the ball all over the field, but looking at a backfield loaded with solid backs and a WR corps headlined by rising outside threat Justin Blackmon, he added in the diamond look, which was simply Nevada's pistol set with an extra fullback flanking the QB:
Lead running back Kendall Hunter then went for 1548 rushing yards at 5.7 yards per pop along with 16 touchdowns. Back-up RB Joseph Randle added another 452 yards and lead WR Justin Blackmon had 1782 yards and a jaw-dropping 20 touchdown receptions.
The diamond formation was a game changer and offenses all over the nation immediately begin installing and tinkering with the set. Spread teams in particular found it to be a godsend as it allowed them to incorporate smashmouth football tactics without having access to big time TE talent major pro-style programs can find.
Now the scheme has grown far beyond what Holgorsen intended for it and has developed a role in a variety of different systems.
Strengths of the diamond formation
The diamond formation has proven useful for a few major philosophical goals:
1. It's great for attacking multiple parts of the line of scrimmage
Loading the backfield with both of your non-OL blockers rather than putting them along the line of scrimmage means there's no telling where they'll be inserted along the line of scrimmage.
Linebackers and safeties know before the snap where they'll be needed against a TE set or a spread alignment but against the diamond set the offense could bring extra blockers just about anywhere and the defenders have to process that information along with everything else that's going on after the snap. That said, their coverage assignments get simpler.
2. It's great for creating misdirection
Since the defense is reading the flow of three different running backs after the snap it's easy for the offense to create false keys and create chaos after the snap before running RB screens, counter plays, reverses, and all manner of misdirecting evil.
3. It creates 1-on-1 match-ups on the outside for star receivers
See Justin Blackmon's huge 2010, or what Holgorsen has since done at West Virginia for outside receivers like Stedman Bailey, Mario Alford, or Kevin White. To get even numbers against the diamond formation the defense generally has to load the box with eight defenders, creating a 1-on-1 outside for someone.
Weaknesses of the diamond formation
There are offenses that won't find much value in the diamond between the 20s, such as older varieties of the Air Raid, West-Coast offenses, or systems that rely heavily on a ball-control passing game.
1. It's a terrible fit for the quick passing game
With four offensive players in the backfield stacked behind the OL, it becomes difficult to get multiple receivers out in routes quickly with leverage against the defensive backfield. Additionally, rules prohibit running twin receiver sets which then severely limits the passing concepts that can be run from the set. You are left with play-action deep shots and rollouts.
2. It's harder to get double teams on the edge
If you have a TE who excels at combo-ing with the offensive tackle to pancake a defensive end and caving in the edge of a defense he's not going to have that same opportunity in the diamond. Similarly, defensive ends who excel at creating havoc against a run game are going to be harder to control unless you have exceptional fullbacks.
The necessary components to build a diamond formation
The diamond is much easier to staff, personnel-wise, than some other formations. There are ideal player-types an offense would love to have to run the system but it can be effective without elite personnel.
1. A good running back
The diamond formation makes its living running the football, if you don't have anyone worth featuring in the run game this isn't the set for you.
2. Lead blockers
Tight ends and H-backs often do fine when positioned more like fullbacks in this set and a running back who can throw a good cut block or stalk a defensive back in addition to running the ball has tremendous value.
The fullback is the ideal player to pair in the backfield with runners in this set but the more versatile the player used as a lead blocker the more dynamic and versatile the formation becomes. Oklahoma's Trey Millard, with his ability to be a lead blocker, catch out of the backfield, and run the ball was an ideal player to feature in the diamond.
3. A vertical threat on the outside who can abuse a 1-on-1 match-up
Otherwise the offense will bring eight or even nine in the box and choke the life out of the system. Plus, running games are always more fun when paired with the possibility of a deep play-action lob that takes the top off the defense.
4. A QB who can throw down the field
So long as he's good enough to get the ball in the hands of a big play receiver on the outside, or else trigger an option-attack, any QB can apply for the role of diamond formation trigger-man.
The ideal diamond personnel would involve the following players:
A versatile fullback who can lead through a hole, trap block a defensive, catch out of the backfield, and be a power-back in short-yardage. Trey Millard is the ultimate example.
An I-formation style lead running back who can also throw a good block on a linebacker or DB on the edge. Examples would include typical big backs like Todd Gurley or Jeremy Langford.
Then, your "Percy Harvin-type" who can motion out and catch a pass, be a decoy, or be a lead runner in a traditional running play.
As in most all systems, a dual-threat QB with a strong arm is ideal whereas on the outside a big-play receiver and a solid slot receiver would be most devastating. If you have the personnel, the diamond can easily be used to run both option and traditional run schemes.
Which offensive systems have been the primary benefactors?
The two main schools of offensive football which have benefitted the most from the advent of the diamond have been the option running teams and the power/play-action systems. In particular, spread passing teams that want to become play-action oriented have found the set most useful.
Power and play-action from the diamond
This was the original intention for the set and the way it's most commonly utilized by teams, particularly spread teams who didn't have great tactics previously for creating a downhill run game to use for setting up play-action.
Thanks to the diamond these teams can now just move over a sturdy linebacker who loves contact but wasn't cracking it on defense or a good walk-on fullback and crash them into the line of scrimmage in front of their tailback and viola! smashmouth football.
Perhaps the best diamond play is a combination of "stretch and hammer" concepts, which are isolation-style lead runs with normal zone stretching blocking:
This play design looks to use the OL to create horizontal stretches for the defense with outside zone style blocking before sending lead blockers through those gaps to take out linebackers. A crafty running back can use his eyes and initial trajectory to set up the linebackers to get blocked before jump cutting and darting through the resulting crease.
Here's the brilliance of this scheme for a spread team, the OL don't have to create displacement with double teams or even necessarily climb up to reach linebackers. They can be massive bodies recruited for their pass protection skills who can just use their feet and girth to screen off DL, the lead blockers and lead runner do the heavy lifting of controlling the linebackers and creating big runs.
What's more, watch how easily this play lends itself to play-action with max protection:
There are limited concepts you can run from the diamond, but if those outside receivers can do a lot of damage running post routes, slants, or comebacks against isolated corners. If the defense is keying the backs for pass or run cues this play will throw them for a loop when it becomes a max protection set with the running back releasing as a checkdown option for the QB.
It's very easy for the extra backs to help in multiple spots along the front in pass protection from this concept and their movements mimic what they'd be doing on a lead run.
Teams can also run power schemes from the diamond although the concert of blocks can become quite complicated when you add pulling linemen. It can serve as a useful set for a power run team or a spread passing team with aspirations of having a downhill run game.
The option game from the diamond
Older football fans will note that the diamond formation closely resembles Darrel K. Royal's Wishbone formation, which dominated football all the way through the 80's, primarily at rival Barry Switzer's Oklahoma program. (Incidentally, the Sooners were also quick to steal and maximize OSU's diamond set)
The design of the wishbone was intended to allow the offense to run the veer, triple-option plays to either side of the formation without tipping their hands through alignment.
Today the diamond serves a similar role and is fantastic for running veer-option style plays.
Here it's drawn up against a modern quarters team playing in nickel personnel. It could be run as a triple option play to either side of the formation or as a "load option" play with one of those backs becoming a lead blocker rather than a running threat.
If one of the backs is also effective as a receiver in space it can also be adopted to combine zone read plays like "Zarc" with quick screen plays if the defense shows structural weakness against one or the other:
If you're a defense that lives off an ability to get extra numbers to the point of attack how are you going to operate against a play-call like that? The offense can pound you up the gut with the zone run to the RB, pop you on the edge with the QB running behind a lead arc block, or force you to beat perimeter blocks and corral a speedster in space.
If all three of those are good players, it's checkmate.
In summation, the diamond lends itself to a variety of ways to attack opponents and that's why you see it involved in so many different teams' offensive packages. Any running team that has good lead blockers can find ways to use this set to attack an opponent with confusing variety and get their players in position to do damage.