Coming off a promising 2014 season and with returning starters littered across the offense and defense, Arkansas looked like a heavyweight contender entering 2015. They had the world's biggest OL, a three-year starter at QB, multiple receivers with experience including a pair of good TEs, and a strong defense that was bringing back enough to at least look competitive.

The season was well set up for Arkansas to start off with a bang and carry an undefeated record and serious momentum into SEC play. They opened against UTEP before hosting Toledo at a "neutral site game" in Little Rock Arkansas and then Texas Tech at home in Fayetteville before kicking off the SEC slate against A&M and their rebuilt and untested defense. UTEP was clearly overmatched and the Toledo Rockets were assumed to be as well while Texas Tech featured a horrendous run defense that was sure to be overwhelmed for a second consecutive year by the brutal Arkansas run game.

Brett Bielema's Hogs started as anticipated, wrecking UTEP 48-13 but then proceeded to score only 12 points in a shocking loss to Toledo and then only 24 in a follow up defeat to Kingsbury's Red Raiders. After losing a third straight against A&M in Dallas most people, myself included, wrote off the Arkansas offense and season.

Then they ripped off yet another eight win season thanks to a 5-3 finish in the SEC and, even more amazingly, finished first in the Offensive S&P rankings with the following profile:

10th in rushing S&P, 1st in passing S&P, 4th on standard downs, 1st on passing downs, 1st in success rate, and 3rd in IsoPPP+

Here's how they pulled this off.

Their offense was fantastic at staying on schedule

Arkansas has a run-centric, pro-style offense that was formerly mixed in with Jim Chaney's passing attack but was tweaked a bit in 2015 to include more simple play-action concepts to allow the run and pass to be more closely integrated. The result was that it became even easier for the Hogs to stay ahead of the chains by mixing their run and pass concepts and mixing in play-action on early downs in ways that allowed them to create easy throws and the potential for big gains.

Take this play-action throw outside to Drew Morgan:

The OL is blocking as though this were an outside zone run but Allen pulls the ball and rolls out opposite the run where they're running a hi-low combination with a TE left in to block for Allen and protect him from facing a contain player running at him to hurry the throw.

Allen then has a hi-lo read on the corner, if he comes up to guard Drew Morgan tight then Allen has to throw it over his head to TE Hunter Henry on a deep out route. Instead the corner is playing soft so Allen hits Morgan underneath the coverage. Then the former two-star receiver shows surprising quicks, makes the corner miss in a veritable broom closet on the sideline, and viola! Six points for Arkansas.

Here's another example of a play that Arkansas liked to use in the red zone:

This time Arkansas is working off their RB draw play, which they often ran with TEs or WRs coming inside and tacking cracks at linebackers who didn't see them coming. This time they have TE Jeremy Sprinkle lined up at fullback and then show the draw play with a WR motioning across the middle.

All of a defenses' experience with the Arkansas run game should tell them to get numbers inside as quickly as possible to stop Alex Collins from thundering up the middle for a TD, but the Hogs have released the fullback, normally a lead blocker, out to the flat. The defenders allow the receiver inside and are drawn in as well to help stop the run and aren't able to recover to keep Sprinkle from beating them outside for an easy pitch and catch touchdown.

This is how you rank first in success rate and third in IsoPPP+, by consistently manufacturing situations where the QB can quickly and easily get the ball to a skill player in space. These days the spread offense is how most teams prefer to accomplish that goal, but Arkansas proves it's also possible within a pro-style system with bigger bodies on the field.

Their run game was designed to generate explosive plays

Arkansas had a fairly diverse run game in 2015 but there was one common feature to a sizable chunk of their playbook, they were excellent at releasing their OL to the 2nd level on most every play. They accomplished this because of two factors, the blocking ability of their tight ends and the tremendous size of their OL.

The Hogs utilized their TEs in the run game in a variety of ways and defenses were virtually never safe from seeing them get involved, sometimes in ways that were hard to pick up on. For instance, the Hogs would run RB draws where H-backs or flex TEs would come inside and pick off linebackers and serve as lead blockers for the back but from unexpected angles.

This is a rare example where they don't get two OL quickly releasing downfield but in exchange for leaving the fantastic left side of their OL at the line, they get a crack block on the weakside linebacker from the TE. They'd also use the TEs to pick off DEs or even DTs on draw and zone plays while releasing their OL down the field to create a veritable moving wall of flesh and pads.

The draw has been the best play in the Hog playbook for the last few years largely because it makes the most of how big and massive their OL is while also making use of Alex Collins' spectacular abilities to set up blocks and also to set up defenders to go outside before cutting back upfield behind the behemoth Hogs in the middle.

As a final reminder, the 2015 Arkansas OL went as follows:

While basking in the glory that one of their OL was literally named "Smothers" take note also of the fact that each of these guys was a gigantic human being that would be both hard to move and hard to resist. What made the draw so perfect for them was that they'd initially take a pass drop step that encouraged the opposing DL to engage with them, and then they'd just lock on and start moving straight ahead.

Because each of these guys was so massive they could usually count being able to control DL without double teams, which meant that these guys were then advancing to the linebackers within a few instants of the ball being snapped.

Of the 271 carries that Collins logged in 2015, 43 of them went for 10 yards or more. That means that almost 16% of the Arkansas running plays were explosive gains. Collins averaged 5.8 yards per carry on the year, despite regularly facing eight man fronts, and it was more than anyone but a few could manage to keep him from running all over them all day long.

They had more than one great receiver

Normally offenses love to complement a great running game with a deep threat receiver they can isolate on the outside to force defenses to either double him and get run over or else single cover him and allow him to have a huge day.

Arkansas didn't really have a deep threat in 2015 but they did have two excellent possession receivers in TE Hunter Henry (51 catches for 739 yards) and WR Drew Morgan (63 catches for 843 yards). It can be feasible to double a single great receiver without exposing yourself to getting obliterated by the run game but it is not possible to focus on a second great receiver, sometimes regardless of whether the run game is even that effective.

The Hogs were excellent on passing downs and they'd often find success by pairing Henry and Morgan within the same concept so that opposing teams couldn't erase one without exposing themselves to the either. Here's a "drive" concept that Arkansas would use with these two players working in conjunction to bind up a pass defense:

You can witness them beat the Mississippi State defense on a 2nd and 5 with this combination here, despite the Bulldogs trying to lock things down with two-deep, man coverage. What got the Bulldogs in trouble was that the weakside linebacker and middle linebacker played over and underneath the shallow cross route by Morgan (X here) and the weakside linebacker drifting to help double Morgan left open a window for Henry on the dig route.

On any concept where Morgan and Henry were paired if the defense cheated towards one receiver it just made for a very easy read and throw to the other. Between that, great protection from a massive OL, and Allen's underrated ability to make throws from a crowded pocket, you had the makings of a no. 1 ranked offense on passing downs.

Arkansas is losing some key coaches and players from the 2015 offense that ultimately proved to be as effective as feared, but it's worth looking back and reflecting on how this unit ultimately came together to form the most underrated offense in college football.