"They've been solid," said O'Brien. "They are not a 2-6 football team. All week long we've talked about how you're not playing a team that is 2-6. You're playing a good football team.
"You've got to be ready to play."
Priority No. 1 for the Wolfpack defense will be stopping a Virginia offense that takes pride in running the football. The Cavaliers feature a pair of diminutive tailbacks in Perry Jones and Kevin Parks who are talented.
"It's always been a big part of Virginia's offense," O'Brien said of Virginia's rushing attack. "When you have all those guys... big guys up front, and you have those shorter backs behind them, hiding behind them. In order for them to be successful they have to run the football, I think.
"They do a good job schematically getting runs on so they are running downhill and in a good position to run. It's going to be tough. We have to get a hold of the line of scrimmage. I think that will be a key for our defense in order to win on Saturday."
"The keys is the running backs, No. 25 (Parks) and No. 33 (Jones)," added defensive coordinator Mike Archer. "We played against them last year, and they're going to feature them. They're going to get their hands on the ball in the running game, and they're going to utilize them in the passing game.
"The main focus, when they've been successful has been their ability to get the ball in the hands of the running backs. They are playmakers in both the passing game and running game."
The problem for Virginia's offense could be the lack of consistency at quarterback. All season long head coach Mike London has had to answer questions about who is or should be his starting quarterback and recently he settled on first-year player Phillip Sims over last year's starter Michael Rocco.
Sims has passed for 660 yards and four touchdowns with just two interceptions in his three game as the starter.
"They're playing with basically (Phillip) Sims as a first-year quarterback," said O'Brien. "The open week can do wonders for a quarterback, to go back, research what he's done. He's got some things in their offense they can correct. It gives chances to the quarterback coach and their offensive staff to emphasize and to make him successful."
Because of the open date Archer believes his unit must prepare for both Rocco and Sims because Virginia could potentially go back to Rocco at the position.
"With an open date, we're not sure who is going to be the quarterback," he said. "The offense doesn't change... now what they call is a little bit different. Rocco started the year, and we played against Rocco last year.
"I believe Sims has started the last three games and then, in the Wake Forest game, Rocco came in at the end and got them back to 16-10. They're a little bit different, but the offense doesn't really change... formation-wise, etc... is not going to change."
While there have been some issues on offense the Cavs have been relatively sound defensively. Virginia is third in the ACC in total defense, allowing 357 yards per game which ranks only behind Florida State and Maryland. The group is led by inside linebacker Steve Greer, one of the ACC's leading tacklers.
"Greer is still the guy in the middle and he runs the operation," said O'Brien. "He's really good. They start a freshman now at defensive end, and they had nothing but juniors and seniors up front with sophomores behind them.. some of the kids played last year.
"They are still the third-best defense statistically in the conference. They are still grudgingly giving up yards and points right now."