This is our first installment of Film Review, our new weekly series where we break down a particular aspect of the weekend's action to help you better understand what's happening on the field.
Run defense has been a constant talking point for the North Carolina football team since the end of last season. The Tar Heels have been gashed on the ground for the past few years, but the final two games of the 2015 season were particularly awful. UNC allowed a total of 964 yards rushing against Clemson and Baylor, giving up an ugly 6.9 yards per carry in two losses.
This year, in defensive coordinator Gene Chizik's second season, the run defense was a point of emphasis throughout the offseason. But in Saturday's 33-24 loss to Georgia, the Tar Heels were run over yet again — surrendering 289 yards on 5.6 yards per attempt. Fifty-five of those yards came on running back Nick Chubb's touchdown run in the fourth quarter that sealed the game for the Bulldogs.
So what happened?
To answer that question, it helps to first understand gap responsibility. Gaps are the spaces between the offensive linemen and are assigned letters: The A-gap is between the center and guard, the B-gap is between the guard and tackle, the C-gap is between the tackle and tight end and the D-gap is everything outside the tight end.
How UNC — and just about every team at every level — defends the run is by assigning each player on defense to a specific gap. Think of it like building a wall along the line of scrimmage. When each player stops up the gap he's responsible for, the result is a wall the offense cannot penetrate.
Of course, the offense's goal is to break through the wall, and they have a variety of strategies to do so. Take Georgia's first play of the game, for instance.
The Bulldogs line up with two tight ends and a fullback pressed close to the line on the right side. Football often boils down to a numbers game — get more players blocking than the opponent has defending. To counteract that, UNC has shifted its formation to the right so linebacker Cayson Collins and cornerback M.J. Stewart are in position if the play runs that way.
However, when the play starts, Georgia has pulled two offensive linemen to the left side of the formation. The remaining linemen block down away from where the play is headed while center Brandon Kublanow (No. 54) will clear out the hole for Chubb by taking out linebacker Cole Holcomb. This is a basic run play called Power that aims to change the numbers advantage in the offense's favor. This time it worked; UNC's defense is now outnumbered.
It's important to note UNC's linebackers here. Holcomb has been neutralized by Kublanow's cut block, while middle linebacker Andre Smith is fighting off a block five yards downfield at the 30-yard line. Neither are in position to stop Chubb.
The very next play, Georgia gives Chubb the ball again.
It's second-and-4 on the second play from scrimmage for Georgia. You can see that the Tar Heels are already desperate to stop the run. They've loaded 10 players into the box — an imaginary region spanning the width of the offensive line and going back five yards. Teams "load the box" to put defenders in better position to defend the run.
The Bulldogs aren't doing anything fancy with this running play. They are pulling a guard and running behind the fullback, challenging UNC to beat them in the trenches and in one-on-one blocks.
North Carolina does a good job on this play of establishing the line of scrimmage and not letting Georgia get too much of a push up front. Holcomb is also pursuing hard on the backside of the play, forcing Chubb to his left.
But Georgia fullback Christian Payne (No. 47) does an excellent job of pancake-blocking the UNC defender — in this case, it's cornerback Des Lawrence.
In this frame, you can see the Georgia blocker lying on top of him at the 37-yard line. That block gives Chubb the lane to break this run to the outside and gain a first down.
This play is a good example of Nick Chubb just being good at what he does. North Carolina doesn’t do a whole lot wrong on this play, but Chubb still makes them pay by using his vision to bounce outside.
It wasn't all bad for UNC's run defense, though. The Tar Heels tend to sacrifice size for speed on defense, particularly in the linebacking corps. Though that hurt them at times on Saturday, it led to a big play here.
Georgia again lines up with three tight ends, a clear sign to UNC that this was going to be a running play. The players on the field often dictate the call: More running backs and tight ends signify a run, while more receivers often indicate a pass.
UNC calls a great play in this case. Georgia is running Power again, pulling the center and tackles to the left while blocking down to the right. But Chizik has sent Andre Smith on a blitz right in the space vacated by center Brandon Kublanow.
One of the best ways to counter when an offense pulls a lineman is to blitz the space he leaves behind. It's tough for the guard to get over in time to stop the defender — especially when the defender is as fast as Smith. The sophomore blows right by the blocker and is in the backfield before Chubb has even taken the handoff.
The play ends in a 5-yard loss for Georgia, one of the few wins for UNC's defense on the night.
In 2015, North Carolina took pride in being a good red-zone defense, with opponents scoring on 48 of 54 (88.9 percent) of drives in the red zone. Georgia was 4-for-4 on Saturday in red-zone scoring, and here’s an example of one of those scores.
Again, it’s a pretty simple running play for Georgia. The Bulldogs pull their right tackle and have tight end Jeb Blazevich (No. 83) set the edge by blocking North Carolina’s defensive end. The running back then runs behind the fullback.
As the play develops, you can see how well it sets up for the running back. Georgia’s blockers are able to get to the linebackers in the second level of the defense with relative ease.
UNC is slow getting to the edge and gives first-year running back Brian Herrien (No. 35) a nice lane to the outside. Somebody needed to get outside and force Herrien back to the middle of the field, where more Tar Heels can collapse for the tackle. Instead, it’s a touchdown for Georgia and a 14-7 lead.
The Bulldogs ran this exact same play late in the fourth quarter. Needing a first down to run out the clock, Georgia got much more.
Everyone in the building knew this was a run play. Georgia lined up in the I-formation — the running back, fullback and quarterback forming the letter 'I' — and UNC put just about everybody into the box. However, the Bulldogs are lined up and ready to go while the Tar Heels are still getting into their stances. They're not ready to play the biggest series of the game.
Before the play begins, Georgia sends Blazevich in motion. At the snap, he'll attack the defensive end with a crack block — a block out of motion coming from the outside of the field — while the right tackle will pull out into space. Notice how Andre Smith is leaning at midfield to the opposite direction the play is headed, putting himself out of position to flow to the ball.
Blazevich is whipping the defensive end in the middle of the picture, while the Georgia receiver has a decent block on safety Dominquie Green in the middle of the Chick-fil-A logo. The fullback and tackle for Georgia are out in space, and the offense has successfully flanked the defense. This is already set up to be a good play.
UNC turns a good play for Georgia into a great one, though, by missing three tackles in quick succession. Holcomb is diving at Chubb's ankles in the current frame; he won't make the tackle. Both Lawrence and safety Donnie Miles make attempts with poor technique, trying to reach and grab Chubb instead of run through him with their bodies. He runs through them easily...
...and is off to the races.
The good news for the Tar Heels is that they won't face a running back like Nick Chubb every week. The bad news is that other teams with less talented runners will still be able to exploit UNC's defense if it continues to play like it did Saturday. North Carolina's defenders were blown out of their gaps too easily too many times. Basic mistakes, like not being ready at the snap and missing tackles, exacerbated the problem. Look for the run defense to still be a sore spot as the season continues.