Last year, ACC offenses never were more efficient during conference play than when they faced Virginia. The Cavaliers allowed opposing ACC offenses, on average, to score a touchdown once every 15.57 snaps. That mark ranked dead last in the conference for a team that went 1-7 in ACC play.

But Virginia registered a remarkable defensive turnaround this season, and that fact is measurable in many ways. The Cavaliers were stingier against the run, stingier on third downs, stingier in the red zone and created more turnovers. But most importantly, the defense more frequently kept opponents out of the end zone, a big reason why Virginia improved to 5-3 in ACC play this season.

Opposing conference offenses needed an average of 23.91 snaps to score a touchdown against the Cavaliers this year, a mark that ranked No. 5 in the ACC. Indeed, the Virginia defense was not elite in this regard by ACC or national standards, but it was far more efficient than it was a season ago.

“From a defensive standpoint, you’ve got to stop your opponent; we all know that,” Defensive coordinator Jim Reid said Thursday. “But how you stop them, where you stop them and then where does the [opposing] offense start their drive? You have to stop the running game first, and we have improved there. We’ve improved greatly there.

“What we’ve been able to do is do a much better job of changing our coverages and adapting them to different motions and different shifts without losing efficiency. We’ve been able to stay with it.”

No ACC defense made opposing offenses more inefficient in conference play this year than Miami, but the Hurricanes – with their 3-5 conference record – were undermined by their own offensive struggles. On average, opposing ACC offenses scored a touchdown against Miami every 29.44 snaps.

That point raises two others: 1) One could make the argument that, across the board this season, either ACC defenses were not as stout or ACC offenses were more efficient this fall. Last year, Boston College allowed opposing ACC offenses to score a touchdown, on average, once every 47.58 snaps. The Eagles were one of five ACC defenses in that category that possessed an average greater than 30.

2) Virginia’s considerable defensive improvement this season would have meant little in terms of the team’s overall stock were it not for the capable performance of its offense. The Cavaliers ranked No. 4 in the ACC in total offense (396.8 yards per game) and, most of the time, scored just enough points to survive.

But back to Virginia’s defense. The Cavaliers have allowed, on average, 75.3 less rushing yards per game this season than they did last year. More importantly, the Virginia defense cut down on the number of big plays it allowed against the run this fall. In 2010, opposing teams tallied 67 rushes of 10 or more yards against the Cavaliers. Virginia trimmed that number to 51 in 2011.

Indeed, the Cavaliers’ defense that is preparing to face Auburn in the Chick-fil-A Bowl on Saturday bears little resemblance to the one that took the field last season. And according to Reid, that has as much to do with familiarity – perhaps the most obvious factor – than anything else.

Last year, Virginia was in the midst of a transition from the 3-4 base defense implemented by former Coach Al Groh to the 4-3 scheme preferred by Reid and Coach Mike London. Now that the players are more comfortable with their assignments, Reid said, they’re starting to churn out more positive results.

“Our players have learned the terminology of our defense, they’ve studied the game so they have an idea of what our opponents are going to do and I just think there’s been a cohesiveness within our group that has been great,” Reid said.

Here’s a rundown of each ACC team’s defensive efficiency rating (the average number of plays it took for opposing offenses to score a touchdown) during conference play in 2011 (asterisk indicates that team earned a bowl berth; Miami had a good enough record for a bowl but chose not to play in one to pre-empt possible NCAA sanctions).

Team Defensive efficiency ACC record
Miami 29.44 3-5
Florida State* 29.21 5-3
Virginia Tech* 26.21 7-1
BC 25.09 3-5
Virginia* 23.91 5-3
N.C. State* 23.23 4-4
Wake Forest* 23.04 5-3
North Carolina* 22.40 3-5
Clemson* 21.80 6-2
Georgia Tech* 19.96 5-3
Maryland 17.50 1-7
Duke 16.64 1-7